Coated metal sheet, method for producing same, and exterior building material

ABSTRACT

This coated metal sheet for exterior covering has a metal sheet and a top coating layer disposed on the metal sheet, the top coating layer is configured from a fluororesin and contains a gloss control agent comprising 0.01-15 vol % of microporous particles and a matte agent comprising primary particles, and the coated metal sheet satisfies the belowmentioned formulae. In the number-based particle size distribution of the gloss control agent and the matte agent, R is the number average particle size (μm) of the gloss control agent, D1 97.5  and D2 97.5  represent the 97.5% particle size (μm) of the gloss control agent and the matte agent, Ru is the upper limit particle size (μm) of the gloss control agent, and T is the top coating layer thickness (μm). 
         D 1 97.5   /T ≦0.9
 
         Ru ≦1.2 T  
 
         R ≧1.0
 
       0.5≦ D 2 97.5   /T ≦7.0
 
       3≦ T ≦40.

TECHNICAL FIELD

The present invention relates to a coated metal sheet for exterior use,a production method therefor, and an exterior building material.

BACKGROUND ART

Coated metal sheets, excellent in versatility, designability, durabilityand the like, have been used in various applications. In coated metalsheets for exterior building material applications, mainly from theviewpoint of designability, a gloss adjusting agent is usually blendedin an overcoat coating film which is a surface of the coated metal sheetsurface. Silica particles are usually used as the gloss adjusting agentin the coated metal sheets for exterior building materials. The particlediameter of the silica particles is usually specified by an averageparticle diameter. The average particle diameter of the silica particlesas the gloss adjusting agent in the coated metal sheet is usually from 3to 30 μm, depending on the color and the application (for example, seePTL 1 (paragraph 0018)). Additionally, in order to provide the coatingfilm with unevenness to thereby provide the appearance and texture of aso-called “matte coated steel sheet”, it is necessary to further add amatting agent having a particle diameter larger than that of the glossadjusting agent. Examples of the type of the matting agent include glassbeads, resin beads and the like. The average particle diameter of thematting agent is usually from 10 to 50 μm (for example, see PTL 2(paragraph 0016)).

CITATION LIST Patent Literature PTL 1

-   Japanese Patent Application Laid-Open No. 2011-148107

PTL 2

-   Japanese Patent Application Laid-Open No. 2004-154993

SUMMARY OF INVENTION Technical Problem

As coated metal sheets for exterior building materials, chromate-coatedsteel sheets are used. Efforts have been made to improve the moldingprocessability or the corrosion resistance at cut ends for thechromate-coated steel sheets, which thus have had long-term durability.Meanwhile, strong interest has been shown to environmental preservationin recent years also in the technical field of exterior buildingmaterials. Accordingly, legal regulations to ban the use of componentsthat adversely affect or cause a concern about possibility of adverselyaffecting the environment have been under consideration. For example,restriction of the use of hexavalent chromium components, generally usedin coated metal sheets as an anti-rust component, in the near future isunder consideration. Also for chromate-free coated steel sheets, variousconsiderations have been made such as pre-coating treatment,optimization of anti-rust pigments and the like, and characteristicsobtained at molding processed portions and cut ends are comparable tothose of the chromate-coated steel sheets.

However, the corrosion resistance of the flat portion in chromate-coatedsteel sheets did not lead to a large problem, while corrosion in theflat portion in chromate-free coated steel sheets may become severe.Particularly when silica particles are used as the gloss adjustingagent, corrosion such as stain rust, coating film blistering and thelike, in the flat portion has occurred during actual use in some cases,before the intended age of service, as shown in FIG. 1.

An object of the present invention is to provide a coated metal sheetand an exterior building material that have matte designability as wellas, even being chromate-free, have excellent flat-portion corrosionresistance equivalent to or greater than that of coated metal sheetscomprising a chromate anti-rust treated metal sheet.

Solution to Problem

The present inventors have intensively studied causes of theaforementioned corrosion in the flat portion. FIG. 2 is a micrograph ofa corroded portion in the flat portion of a chromate-free coated metalsheet. In FIG. 2, portion A is a portion where silica particles as agloss adjusting agent are exposed from the overcoat coating film, andportion B is a portion where the silica particles have fallen off fromthe overcoat coating film. FIG. 3 is a reflection electron micrograph ofa cross section along line L, in FIG. 2, in portion A of the coatedmetal sheet. FIG. 4 is a reflection electron micrograph of a crosssection along line L, in FIG. 2, in portion B of the coated metal sheet.FIG. 3 clearly shows the occurrence of cracks at the silica particlesexposed on the surface of the overcoat coating film, and FIG. 4 clearlyshows that corrosion of the metal sheet originates from the holes in theovercoat coating film from which the silica particles have fallen off.

As described above, the present inventors have confirmed that, whenparticles having micropores such as silica are used as the glossadjusting agent, the corrosion occurs in a portion where the glossadjusting agent in the overcoat coating film has cracked, collapsed, orfallen off, and also that the gloss adjusting agent exposed from theovercoat coating film to be worn in actual use cracks, collapses andfalls off from the overcoat coating film.

The present inventors have also investigated the gloss adjusting agentto thereby confirm that the silica particles specified by an averageparticle diameter contain particles considerably larger than the averageparticle diameter relative to the thickness of the overcoat coatingfilm. For example, when observing, among commercially available silicaparticles to be used as the gloss adjusting agent, silica particleshaving an average particle diameter of 3.3 μm with an electronmicroscope, the present inventors have confirmed that silica particleshaving a particle diameter of about 15 μm are contained (FIG. 5).Additionally, the present inventors have observed the surface of thesilica particles (portion B in FIG. 6A) and have confirmed thatnumberless minute gaps, which are specific to aggregated particles, areopen to the surface (FIG. 6B).

Furthermore, the present inventors have confirmed that abrasion of theovercoat coating film and falling-off of the gloss adjusting agentsimilarly as aforementioned occur even in an overcoat coating filmcomposed of fluorine resin, which has generally excellent weatherability(FIGS. 7A and 7B) although the phenomena are milder than those in anovercoat coating film composed of ordinary resin such as polyester. InFIG. 7A, the holes formed in the overcoat coating film are shown asblack points. The holes have resulted from falling-off of the glossadjusting agent from the overcoat coating film as shown in FIG. 7B.

Similarly when aggregated particles such as silica, polyacrylonitrile(PAN) and the like are used as a matting agent to be additionally usedin the overcoat coating film, the present inventors have also confirmedthat corrosion originates in a portion where the matting agent exposedfrom the overcoat coating film has cracked, collapsed, or fallen off(FIG. 8 and FIG. 9).

Then, the present inventors, focusing on the fact that such aggregatedparticles having a large particle diameter decrease the corrosionresistance, have found that, by use of a gloss adjusting agent having aspecific particle diameter relative to the thickness of the overcoatcoating film and a matting agent, corrosion resistance can be obtainedequivalent to or greater than the corrosion resistance achieved bychromate-based chemical conversion treatment and by use of achromium-containing anti-rust pigment in an undercoat coating film inconventional metal sheets, having completed the present invention.

Thus, the present invention relates to a coated metal sheet and anexterior building material below.

[1] A coated metal sheet including: a metal sheet, and an overcoatcoating film disposed on the metal sheet, in which the overcoat coatingfilm is composed of fluorine resin, and the overcoat coating filmcomprises a gloss adjusting agent which is particles having microporesand a matting agent which is primary particles, in which a content ofthe gloss adjusting agent in the overcoat coating film is from 0.01 to15 vol %, in which a content of the matting agent in the overcoatcoating film is from 0.01 to 15 vol %, and in which the coated metalsheet satisfies the following equations:

D1_(97.5) /T≦0.9

Ru≦1.2T

R≧1.0

0.5≦D2_(97.5) /T≦7.0

3≦T≦40

in which R (μm) is a number average particle diameter of the glossadjusting agent, T (μm) is a film thickness of the overcoat coatingfilm, D1_(97.5) (μm) is a 97.5% particle diameter in an accumulatedparticle size distribution of the gloss adjusting agent based on thenumber of particles, D2_(97.5) (μm) is a 97.5% particle diameter in anaccumulated particle size distribution of the matting agent based on thenumber of particles, and Ru (μm) is an upper limit particle diameter ina number particle size distribution of the gloss adjusting agent.[2] The coated metal sheet according to [1], in which the Ru is lessthan T.[3] The coated metal sheet according to [1] or [2], in which the metalsheet has been subjected to non-chromate anti-rust treatment, and thecoated metal sheet is chromate-free.[4] The coated metal sheet according to [1] or [2], in which the metalsheet has been subjected to chromate anti-rust treatment.[5] The coated metal sheet according to any one of [1] to [4], in whichthe gloss adjusting agent is silica particles.[6] The coated metal sheet according to any one of [1] to [5], furtherincluding an undercoat coating film between the metal sheet and theovercoat coating film.[7] The coated metal sheet according to [6], further including anintercoat coating film between the undercoat coating film and theovercoat coating film.[8] The coated metal sheet according to any one of [1] to [7], in whichthe overcoat coating film is composed of a resin component, as the maincomponent, comprising polyvinylidene fluoride and acrylic resin.[9] The coated metal sheet according to in any one of [1] to [8], havinga glossiness at 60° is 0.1 to 15.[10] The coated metal sheet according to in any one of [1] to [9], beinga coated metal sheet for exterior use.[11] An exterior building material comprising the coated metal sheetaccording to any one of [1] to [9].

Also, the present invention relates to a method for producing a coatedmetal sheet below.

[12] A method for producing a coated metal sheet having a metal sheetand an overcoat coating film disposed on the metal sheet, including thesteps of: applying an overcoat coating material containing a fluorineresin, a gloss adjusting agent, and a matting agent onto the metalsheet; and curing the coating film of the overcoat coating material toform the overcoat coating film; in which a content of the glossadjusting agent in the overcoat coating film is from 0.01 to 15 vol %,and a content of the matting agent in the overcoat coating film is from0.01 to 15 vol %, in which the gloss adjusting agent is particles havingmicropores, and the matting agent is primary particles, and in which thegloss adjusting agent and the matting agent which satisfy the followingequations are employed:

D1_(97.5) /T≦0.9

Ru≦1.2T

R≧1.0

0.5≦D2_(97.5) /T≦7.0

3≦T≦40

in which R (μm) is a number average particle diameter of the glossadjusting agent, T (μm) is a film thickness of the overcoat coatingfilm, D1_(97.5) (μm) is a 97.5% particle diameter in an accumulatedparticle size distribution of the gloss adjusting agent based on thenumber of particles, D2_(97.5) (μm) is a 97.5% particle diameter in anaccumulated particle size distribution of the matting agent based on thenumber of particles, and Ru (μm) is an upper limit particle diameter ina number particle size distribution of the gloss adjusting agent.[13] The method for producing a coated metal sheet according to [12], inwhich the overcoat coating material has been subjected to treatment forpulverizing the particles in the overcoat coating material.

Advantageous Effects of Invention

The present invention prevents exposure, cracking and the like of thegloss adjusting agent, and cracking, fall-off and the like of thematting agent, at the intended age of service. As a result, there isprovided a coated metal sheet that has intended matte designabilityhaving an adjusted gloss as well as, although being chromate-free, hasexcellent flat-portion corrosion resistance equivalent to or greaterthan that of coated metal sheets comprising a chromate anti-rust treatedmetal sheet.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a micrograph of a corroded portion (coating film blistering)occurring in the flat portion of a chromate-free coated metal sheet inactual use of five years;

FIG. 2 is a micrograph of a corroded portion in the flat portion of thechromate-free coated metal sheet;

FIG. 3 is a reflection electron micrograph of a cross section along lineL, in FIG. 2, in portion A of the coated metal sheet shown in FIG. 2;

FIG. 4 is a reflection electron micrograph of a cross section along lineL, in FIG. 2, in portion B of the coated metal sheet shown in FIG. 2;

FIG. 5 is an electron micrograph of commercially available silicaparticles having an average particle diameter of 3.3 μm;

FIG. 6A is an electron micrograph of commercially available silicaparticles, and FIG. 6B is an enlarged electron micrograph of portion Bin FIG. 6A;

FIG. 7A is an enlarged electron micrograph of a part of the flat portionin a chromate-free and fluorine-resin overcoat coating film on thecoated metal sheet in actual use of 7.5 years, shown at a magnificationof 250, and FIG. 7B is an enlarged electron micrograph of the part ofthe flat portion, shown at a magnification of 1,000;

FIG. 8 is a micrograph of a cross section of a corroded portion in theflat portion of a chromate-free coated metal sheet in which silicaparticles are used as a matting agent; and

FIG. 9 is a micrograph of a cross section of a corroded portion in theflat portion of a chromate-free coated metal sheet in which PANparticles are used as a matting agent.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the coated metal sheet according to one embodiment of thepresent invention will be described. The coated metal sheet includes ametal sheet and an overcoat coating film disposed on/above the metalsheet.

The metal sheet can be selected from known metal sheets as far as theeffect of the present embodiment can be achieved. Examples of the metalsheet include cold-rolled steel sheets, galvanized steel sheets, Zn—Alalloy-plated steel sheet, Zn—Al—Mg alloy-plated steel sheets,aluminum-plated steel sheets, stainless steel sheets (includingaustenitic, martensitic, ferritic, and ferrite-martensite two-phasesystems), aluminum sheets, aluminum-alloy sheets, copper sheets and thelike. The metal sheets are preferably plated steel sheets from theviewpoint of corrosion resistance, lighter weight, andcost-effectiveness. The plated steel sheet is preferably hot-dip 55%Al—Zn alloy-plated steel sheets, Zn—Al—Mg alloy-plated steel sheets, oraluminum-plated steel sheets, particularly from the viewpoint ofcorrosion resistance and from the viewpoint of suitability for exteriorbuilding materials.

The metal sheet preferably has a chemical conversion film on itssurface, from the viewpoint of improving the adhesiveness of the coatedmetal sheet and the corrosion resistance. Chemical conversion is onetype of pre-coating treatment for metal sheets, and a chemicalconversion film is a composition layer formed by the pre-coatingtreatment. The metal sheets are preferred in that the sheets have beensubjected to non-chromate anti-rust treatment from the viewpoint ofreducing environmental loads in production and use of the coated metalsheet, and in that the sheets have been subjected to chromate anti-rusttreatment from the viewpoint of further improving the corrosionresistance.

Examples of the chemical conversion film by the non-chromate anti-rusttreatment include Ti—Mo composite films, fluoro acid-based films,phosphate films, resin-based films, resin andsilane-coupling-agent-based films, silica-based films, silica andsilane-coupling-agent-based films, zirconium-based films, and zirconiumand silane-coupling-agent-based films.

From the above-described viewpoint, the amount of the Ti—Mo compositefilm deposited is preferably 10 to 500 mg/m² in terms of total Ti andMo, the amount of the fluoro acid film deposited is preferably 3 to 100mg/m² in terms of fluorine or in terms of total elemental metals, andthe amount of the phosphate film deposited is preferably 0.1 to 5 g/m²in terms of elemental phosphorous, on the metal sheet.

The amount of the resin-based film deposited is preferably 1 to 500mg/m² in terms of the resin, the amount of the resin and silane couplingagent-based film deposited is preferably 0.1 to 50 mg/m² in terms of Si,the amount of the silica-based film deposited is preferably 0.1 to 200mg/m² in terms of Si, the amount of the silica and silane couplingagent-based film deposited is preferably 0.1 to 200 mg/m² in terms ofSi, the amount of the zirconium-based film deposited is preferably 0.1to 100 mg/m² in terms of Zr, and the amount of the zirconium and silanecoupling agent-based film deposited is preferably is 0.1 to 100 mg/m² interms of Zr.

Also, examples of the chromate anti-rust treatment include coating-typechromate treatment and phosphate-chromate-based treatment. From theabove-described viewpoint, the amount of the film deposited by thechromate anti-rust treatment on the metal sheet is preferably from 20 to80 g/m² in terms of element chromium.

The overcoat coating film is composed of fluorine resin. The overcoatcoating film may further contain other resin as long as the filmcontains fluorine resin as the main component. For example, the overcoatcoating film may be composed of 50 to 85 mass % of fluorine resin basedon the resin component in the overcoat coating film and the balance ofacrylic resin. The resins in the resin component may or may not bind toeach other.

The fluorine resin has excellent durability, chemical resistance, heatresistance, abrasion resistance, contamination resistance, and the like.Above all, the resin is preferably polyvinylidene fluoride (PVDF)because PVDF has high processability and mechanical strength.

The acrylic resin contributes to an increase in coating-filmadhesiveness. The acrylic resin is preferably thermoplastic acrylicresin or thermosetting acrylic resin, which has compatibility withpolyvinylidene fluoride. Examples of the acrylic resin include polymersof an acrylic monomer, such as methyl methacrylate (MMA), methylacrylate (MA), ethyl acrylate (EA), butyl acrylate (BA) and butylmethacrylate (BMA), or copolymers of monomers including the acrylicmonomers.

The overcoat coating film is preferably composed of a resin componentcomprising polyvinylidene fluoride and acrylic resin as the maincomponent from the above-described viewpoint. In this case, the massratio between polyvinylidene fluoride (PVDF) and the acrylic resin (AR),(PVDF:AR) is preferably in the range of 50:50 to 85:15. When the massratio of polyvinylidene fluoride is extremely low, the properties of thefluorine resin such as weather resistance, corrosion resistance, andcontamination resistance may not be sufficiently exerted. When the massratio of polyvinylidene fluoride is extremely high, the adhesiveness ofthe overcoat coating film may decrease, and thus the processability ofthe coated metal sheet may decrease.

The film thickness T of the overcoat coating film is from 3 to 40 μm. Anextremely large film thickness T of the overcoat coating film may beresponsible for occurrence of defective coating (foaming), reduction inthe productivity, increase in the production cost and the like, whereas,with an extremely small film thickness T, the intended designability andthe intended flat portion-corrosion resistance may not be achieved. Forexample, in order to obtain a coated metal sheet that has goodproductivity, exhibits the intended gloss and coloring, and can beactually used as an exterior building material for at least 10 years,the film thickness T of the overcoat coating film is, for example,preferably 10 μm or more, more preferably 15 μm or more, and still morepreferably 25 μm or more from the above-described viewpoint. Also due tothe above-described reason, the film thickness T of the overcoat coatingfilm is preferably 35 μm or less, more preferably 30 μm or less. Thefilm thickness T of the overcoat coating film is, for example, theaverage value of distances from the bottom to the surface at a pluralityof positions on a portion where the matting agent of the overcoatcoating film is not present.

Alternatively, when the coated metal sheet has other coated film(s)other than the overcoat coating film, the film thickness T of theovercoat coating film can be determined in further consideration of theother coated film(s). For example, when the coated metal sheet has anundercoat coating film described below and the overcoat coating film,the film thickness T of the overcoat coating film is preferably from 10to 30 μm from the viewpoint of the designability, corrosion resistance,and processability. Alternatively, when the coated metal sheet has theundercoat coating film, an intercoat coating film described below, andthe overcoat coating film, the film thickness T of the overcoat coatingfilm is preferably from 3 to 15 μm, from the above-described viewpoint.

The film thickness T of the overcoat coating film is, from the viewpointof the designability of the coated metal sheet, preferably larger when acolor of the overcoat coating film is light, and can be smaller when thecolor of the overcoat coating film is dark. Although it depends on thecase, for example, when the value L of the overcoat coating film is 70or less, the film thickness T of the overcoat coating film can be 20 μmor less, and when the value L of the overcoat coating film is more than80, the film thickness is preferably 25 μm or more.

Alternatively, the film thickness T of the overcoat coating film can besmaller, as the color of the overcoat coating film is closer to thecolor of the surface of the steel sheet before the overcoat coating filmis formed (for example, an undercoat coating film described below), fromthe viewpoint of the designability of the coated metal sheet. Althoughit depends on the case, for example, when the absolute value ΔL of thedifference between the value L of the overcoat coating film and thevalue L of the color of the surface of the steel sheet before thecoating film is formed is 10 or less, the film thickness T of theovercoat coating film can be 13 μm or less, when ΔL is 20 or less, thefilm thickness T can be 15 μm or less, and when ΔL is 50 or less, thefilm thickness T can be 17 μm or less.

Incidentally, the value L can be determined by calculation by theHunter's color difference formula from the measurement result by acommercially available spectrophotometer (for example, manufactured byKONICA MINOLTA OPTICS, INC. “CM3700d”).

The overcoat coating film contains a gloss adjusting agent. The glossadjusting agent is contained in the overcoat coating film to moderatelyroughen the surface of the overcoat coating film for the purpose toachieve the intended gloss in the coated metal sheet, for the purpose toadjust variation of gloss among production lots and the like, impartingthe intended appearance with gloss to the coated metal sheet.

The gloss adjusting agent has a number average particle diameter R(hereinafter, may be also referred to as “R1”) of 1.0 μm or more. Whenthe gloss adjusting agent is extremely small, the gloss of the overcoatcoating film is extremely high, and thus, the intended designability maynot be achieved. As such, it is possible to determine the number averageparticle diameter of the gloss adjusting agent R1 as appropriatedepending on the intended designability (glossiness) of the coated metalsheet as far as R1 satisfies the formula described below. However, whenR1 is extremely large, the roughness of the overcoat coating filmincreases, and thus the intended designability cannot be achieved. Forexample, from the viewpoint of obtaining a coated metal sheet having aglossiness at 60° of 0.1 to 15 in addition to flat-portion corrosionresistance, the number average particle diameter R1 of the glossadjusting agent is preferably 2.0 μm or more, more preferably 3.0 μm ormore, still more preferably 5.0 μm or more, or still even morepreferably 7.0 μm or more. The number average particle diameter can beconfirmed by observation of the cross-section of the overcoat coatingfilm or can be measured by an image analyzing method and the Coultermethod (for example, using an accurate particle sizing and countinganalyzer “Multisizer 4” manufactured by Beckman Coulter Inc.).

Alternatively, when the coated metal sheet has other coated film(s)other than the overcoat coating film, the number average particlediameter R1 of the gloss adjusting agent can be determined depending onthe film thickness T of the overcoat coating film. For example, when thecoated metal sheet has an undercoat coating film and an overcoat coatingfilm, the number average particle diameter R1 of the gloss adjustingagent is preferably 2.0 μm or more, from the viewpoint of thedesignability by the intended gloss, corrosion resistance, andprocessability. Alternatively, when the coated metal sheet has theundercoat coating film, an intercoat coating film described below, andthe overcoat coating film, the number average particle diameter R1 ofthe gloss adjusting agent is 1.0 μm or more, from the above-describedviewpoint.

The content of the gloss adjusting agent in the overcoat coating film is0.01 to 15 vol %. When the content is extremely high, the gloss of theovercoat coating film becomes extremely low, and also, theprocessed-part adhesiveness decreases. When the content is extremelylow, the gloss may not be controlled. Thus, even if the content isextremely large or small, the intended designability may not beachieved. For example, from the viewpoint of obtaining a coated metalsheet having a glossiness at 60° of 0.1 to 15, the content of the glossadjusting agent in the overcoat coating film is preferably 0.05 vol % ormore, more preferably 0.1 vol % or more. Also from the above-describedreason, the content of the gloss adjusting agent in the overcoat coatingfilm is preferably 13 vol % or less, more preferably 10 vol % or less.The content can be confirmed by measurement of the ash content in theovercoat coating film, collection of the gloss adjusting agent bydissolution of the overcoat coating film, image analysis of across-sectional image of element discrimination conducted at a pluralityof points or the like.

The gloss adjusting agent is particles having micropores (hereinafter,may be referred to as “microporous particles”). Examples of themicroporous particles include aggregates formed by chemical bonding ofprimary particles, agglomerates formed by physical bonding of primaryparticles, and porous particles. The porous particles have a porousstructure at least inside the particles. The gloss adjusting agent maybe composed solely of the microporous particles or may contain particlesother than microporous particles. The microporous particles may beinorganic particles or organic particles, and can be selected from knownmicroporous particles used as a gloss adjusting agent, as far as theparticles satisfy the equation described below. Examples of thematerials of the microporous particles include silica, calciumcarbonate, barium sulfate, polyacrylonitrile, and calciumcarbonate-calcium phosphate composites. The gloss adjusting agent ispreferably silica particles from the viewpoint of having a high functionof adjusting the gloss of coated metal sheets.

The coated metal sheet satisfies the following equation:

D1_(97.5) /T≦0.9

wherein R1 is the number average particle diameter of the glossadjusting agent (μm), T is the film thickness of the overcoat coatingfilm (μm), and D1_(97.5) is the 97.5% particle diameter (μm) in theaccumulated particle size distribution of the gloss adjusting agentbased on the number of particles (hereinafter, may also be referred toas “number particle size distribution”). However, when the upperparticle size of the number particle size distribution of the glossadjusting agent is set to Ru (μm), the corresponding Ru is 1.2T or less.“Upper limit particle diameter (Ru)” is a particle diameter when theparticle size distribution curve in the number particle sizedistribution meets the baseline at the number average particle diameterR1 or more.

D1_(97.5) will be a substantial index of the particle diameter of thegloss adjusting agent by which the effect of the present invention isachieved. With extremely large D1_(97.5)/T, the microporous particlesmay be exposed due to wearing of the overcoat coating film during actualuse, and the intended flat portion-corrosion resistance may not beachieved. With extremely small D1_(97.5)/T, the intended glossiness maynot be achieved.

For example, from the viewpoint of obtaining a coated metal sheet havinga glossiness at 60° of 0.1 to 15, D1_(97.5)/T is preferably 0.2 or more,more preferably 0.4 or more. Additionally, from the viewpoint ofobtaining a coated metal sheet having an actual age of service as anexterior building material of at least 10 years or more, D1_(97.5)/T ismore preferably 0.7 or less, still more preferably 0.5 or less.

Meanwhile, in the corresponding number particle size distribution, thecontent of the particles larger than D1_(97.5) is only about 2.5% basedon the number of all the particles. Thus, a gloss adjusting agent ofwhich particle size distribution curve exhibits specific sharpness at aparticle diameter of the number average particle diameter R1 or more inthe number particle size distribution, satisfying “D1_(97.5)/T≦0.9”, canbe applied as it is to the present invention. In other words, the glossadjusting agent having a meeting point (Ru) of 1.2T or less, at whichthe particle size distribution curve in the number particle sizedistribution meets the baseline of the number particle size distributionat the number average particle diameter R1 or more, which satisfies“D1_(97.5)/T≦0.9”, can be applied to the present invention.

The reason why sufficient flat portion-corrosion resistance is exhibitedeven when the upper limit particle diameter Ru (μm) is 1.2T or less(even when more than 0.9T) can be assumed as follows. First, in theovercoat coating film, the resin composition of the overcoat coatingfilm is superposed on the gloss adjusting agent, and thus, it isconceivable that a gloss adjusting agent having a particle diameter of1.2T or less normally may not be exposed from the surface of theovercoat coating film. Alternatively, particles having a particlediameter larger than 0.9T in the gloss adjusting agent are unlikely todeviate from the normal distribution so significantly, even if theactual number particle size distribution described above in the rangelarger than the R1 deviates from the normal distribution. Thus, it isconceivable that the content of the particles will be less than 2.5% atmost based on the total. Therefore, it is conceivable that particleshaving a particle diameter larger than 0.9T in the gloss adjusting agentmay be too small in number to substantially influence the flatportion-corrosion resistance. Moreover, the gloss adjusting agent isoddly shaped in general, and usually flattened to some extent.Conceivably, in the gloss adjusting agent in the overcoat coating film,usually the longitudinal direction of the gloss adjusting agent tends tobe oriented to the horizontal direction more than the vertical directiondue to the application of the overcoat coating material described below,and thus, the particle diameter in the in film-thickness direction inthe gloss adjusting agent in the overcoat coating film usually becomesshorter than the long diameter of the gloss adjusting agent (forexample, 1.2T).

When the Ru is extremely large, the microporous particles are exposeddue to wearing of the overcoat coating film during actual use, and theintended flat portion-corrosion resistance may not be obtained. From theviewpoint of obtaining a coated metal sheet having an actual age ofservice as an exterior building material of at least 10 years or more,Ru is preferably less than T, more preferably 0.9T or less, still morepreferably 0.7T or less. R1, D1_(97.5), and Ru can be determined fromthe number particle size distribution of the gloss adjusting agent.

Incidentally, the side smaller than the average particle diameter R1 inthe number particle size distribution of the gloss adjusting agent maybe in any mode as long as the conditions of the particle sizedistribution are satisfied.

As the gloss adjusting agent that satisfies the conditions according tothe particle size distribution, commercially-available products andclassified materials thereof can be used.

Incidentally, to produce the coated metal sheet, the gloss adjustingagent may not satisfy the particle size conditions aforementioned (forexample, coarse particles larger than 1.2T are present and the like), ormay deviate from the above-described conditions in the process ofproduction. In this case, a step of pulverizing the coarse particles inthe overcoat coating material described below, such as roller milltreatment as described below, is suitably performed from the viewpointof obtaining the coated metal sheet.

The overcoat coating film also contain a matting agent. The mattingagent is contained to the overcoat coating film in order to exhibitunevenness that is larger than the coarseness to be imparted by a glossadjusting agent to the overcoat coating film and can be visuallyconfirmed and to impart a texture, providing the coated metal sheet withthe intended appearance. The matting agent also includes those having aparticle diameter larger than the film thickness of the overcoat coatingfilm, and thus can prevent the overcoat coating film from beingscratched. Thereby, the scratch resistance of the coated metal sheet canbe improved.

Although the number average particle diameter of the matting agent(hereinafter, may be also referred to as “R2”) is not particularlylimited, the matting agent having an extremely small particle diametercannot reduce the gloss of the overcoat coating film, and the intendeddesignability may not be achieved. It is possible to determine thenumber average particle diameter of the matting agent R2 as appropriatedepending on the intended designability (glossiness) of the coated metalsheet as far as R2 satisfies the equation described below. However, whenR2 is extremely large, the matting agent causes streaks on coating, andthe intended designability may not be achieved. For example, to obtain acoated metal sheet having a glossiness at 60° of 0.1 to 15 in additionto flat-portion corrosion resistance, the number average particlediameter R2 of the matting agent is preferably 5.0 μm or more, morepreferably 10.0 μm or more, still more preferably 15.0 μm or more, evenmore preferably 20 μm or more, still even more preferably 25 μm or more.Also, due to the above-described reason, the number average particlediameter of the matting agent R2 is preferably 80 μm or less, morepreferably 50 μm or less, still more preferably 40 μm or less. Thenumber average particle diameter can be confirmed by observation of thecross-section of the overcoat coating film or can be measured by animage analyzing method and the Coulter method (for example, using anaccurate particle sizing and counting analyzer “Multisizer 4”manufactured by Beckman Coulter Inc.).

The content of the matting agent in the overcoat coating film is 0.01 to15 vol %. When the content is extremely high, the gloss of the overcoatcoating film decreases, and also, the processed-part adhesivenessdecreases. In contrast, when the content is extremely low, gloss cannotbe adjusted, and in both cases, the intended designability may not beachieved. For example, from the viewpoint of obtaining a coated metalsheet having a glossiness at 60° of 0.1 to 15, the content of thematting agent in the overcoat coating film is preferably 0.1 vol % ormore. Also due to the above-described reason, the content of the mattingagent in the overcoat coating film is preferably 13 vol % or less, morepreferably 10 vol % or less. The content can be confirmed by measurementof the ash content in the overcoat coating film, collection of thematting agent by dissolution of the overcoat coating film, imageanalysis of a cross-sectional image of element discrimination conductedat a plurality of points or the like.

The matting agent is primary particles. The primary particles refer toparticles having no micropores that may cause the particles to collapsewhen the substance (for example, water) present in their voids expands.The primary particles may be resin particles or inorganic particles, andcan be selected from known primary particles used as a matting agent, asfar as the particles satisfy the equation described below. Specificexamples of the primary particles include primary particles composed ofresin such as acrylic resin, polyurethane resin, polyester resin,melamine resin, urea resin, polyamide resin and the like (resinparticles); and primary particles composed of an inorganic compound suchas glass, silicon carbide, boron nitride, zirconia, alumina, silica, andthe like (inorganic particles). The shape of these primary particles ispreferably approximately spherical, but may be other shape such as acylindrical shape, a disc shape and the like. Also, recesses and thelike may be present on the surface of the primary particles unless theyare micropores that may become an origin of collapse of the particles.

The coated metal sheet satisfies the following equation:

0.5≦D2_(97.5) /T≦7.0

wherein T (μm) is the film thickness of the overcoat coating film, andD2_(97.5) is the 97.5% particle diameter (μm) in the accumulatedparticle size distribution of the matting agent based on the number ofparticles.

D2_(97.5) will be a substantial index of the particle diameter of thematting agent by which the effect of the present invention is achieved.When D2_(97.5)/T is extremely large, streaks or the like attributable tothe matting agent occur on coating of the overcoat coating film, and afair coating appearance may not be achieved. When D2_(97.5)/T isextremely small, the intended texture may not be achieved.

For example, from the viewpoint of obtaining a coated metal sheet havinga glossiness at 60° of 0.1 to 15, D2_(97.5)/T is preferably 1 or more,more preferably 2 or more, even more preferably 3 or more, still evenmore preferably 4 or more. Additionally, for example, from the viewpointof obtaining a coated metal sheet having an actual age of service as anexterior building material of at least 10 years or more, D2_(97.5)/T ispreferably 6 or less, more preferably 5 or less. R2 and D2_(97.5) can bedetermined from the number particle size distribution of the mattingagent.

The overcoat coating film may further contain other ingredients besidesthe resin, gloss adjusting agent, and matting agent aforementioned, asfar as the effect of the present embodiment can be achieved. Forexample, the overcoat coating film may further contain a colorant.Examples of the colorant include inorganic pigments such as titaniumoxide, calcium carbonate, carbon black, iron black, iron oxide yellow,titanium yellow, colcothar, iron blue, cobalt blue, cerulean blue,ultramarine blue, cobalt green, molybdenum red and the like; compositeoxide calcined pigments containing metal components such as CoAl,CoCrAl, CoCrZnMgAl, CoNiZnTi, CoCrZnTi, NiSbTi, CrSbTi, FeCrZnNi,MnSbTi, FeCr, FeCrNi, FeNi, FeCrNiMn, CoCr, Mn, Co, SnZnTi and the like;metallic pigments such as Al flakes, resin-coated Al flakes, Ni flakes,stainless flakes and the like; and organic pigments such as QuinacridoneRed, Lithol Red B, Brilliant Scarlet G, Pigment Scarlet 3B, BrilliantCarmine 6B, Lake Red C, Lake Red D, Permanent Red 4R, Bordeaux 10B, FastYellow G, Fast Yellow 10G, Pare Red, Watching Red, Benzidine Yellow,Benzidine Orange, Bon Maroon L, Bon Maroon M, Brilliant Fast Scarlet,Vermilion Red, Phthalocyanine Blue, Phthalocyanine Green, Fast Skyblue,Aniline Black and the like. The colorant is sufficiently smallerrelative to the gloss adjusting agent, and, for example, the numberaverage particle diameter of the colorant is 0.01 to 1.5 μm. The contentof the colorant in the overcoat coating film is, for example, 2 to 20vol %.

The overcoat coating film may further contain an extender pigment.Examples of the extender pigment include barium sulfate and titaniumoxide. The extender pigment is sufficiently smaller relative to thegloss adjusting agent, and, for example, the number average particlediameter of the extender pigment is 0.01 to 1 μm. The content of theextender pigment in the overcoat coating film is, for example, 0.1 to 15vol %.

The overcoat coating film may further contain a lubricant, from theviewpoint of preventing the occurrence of galling in the overcoatcoating film on processing the coated metal sheet. Example of thelubricant include organic waxes such as fluorine-based wax,polyethylene-based wax, styrene-based wax, polypropylene-based wax andthe like, and inorganic lubricants such as molybdenum disulfide, talcand the like. The content of the lubricant in the overcoat coating filmis, for example, 0 to 10 vol %.

The overcoat coating film is produced by a known method that includesapplying a coating material for overcoat coating films (overcoat coatingmaterial) to the surface of the metal sheet, the surface of theundercoat coating film described below or the like, drying the coatingmaterial, and curing the coating material as required. The overcoatcoating material contains materials for the overcoat coating filmaforementioned, and may further contain other ingredients besides thematerials as far as the effect of the present embodiment can beachieved.

For example, the overcoat coating material may further contain a curingagent. The curing agent crosslinks the fluorine resin or acrylic resinaforementioned on curing (baking) when the overcoat coating film isproduced. The type of the curing agent can be selected from thecrosslinking agent aforementioned and known curing agents asappropriate, depending on the type of the resin to be used, bakingconditions and the like.

Examples of the curing agent include melamine compounds, isocyanatecompounds, combinations of a melamine compound and an isocyanatecompound and the like. Examples of the melamine compound include iminogroup-type, methylol-imino group-type, methylol group-type, or completealkyl group-type melamine compounds. The isocyanate compound may be anyof aromatic, aliphatic, and alicyclic compounds, and examples includem-xylene diisocyanate, hexamethylene diisocyanate, naphthalenediisocyanate, isophorone diisocyanate, and block compounds of these.

The overcoat coating film may further contain a curing catalyst asappropriate as far as the storage stability of the overcoat coatingmaterial is not affected. The content of the curing agent in theovercoat coating film is for example, 10 to 30 vol %.

The overcoat coating film may also contain 10 vol % or less of anultraviolet absorber (UVA) or a light stabilizer (HALS) as appropriatein order to further improve the weather resistance. Furthermore, theovercoat coating film may contain a hydrophilizing agent, for example,30 vol % or less of a partially hydrolyzed condensate oftetraalkoxysilane for prevention of rain streak stains.

The coated metal sheet may have further components, as far as the effectof the present embodiment can be exerted. For example, the coated metalsheet preferably further may have an undercoat coating film between themetal sheet and the overcoat coating film, from the viewpoint ofimproving the adhesiveness and the corrosion resistance of the overcoatcoating film in the coated metal sheet. The undercoat coating film isdisposed on the surface of the metal sheet, or, when the chemicalconversion film has been made, on the surface of the chemical conversionfilm.

The undercoat coating film is composed of resin. Examples of the resininclude epoxy resin, polyester, epoxy-modified polyester resin, acrylicresin, and phenoxy resin.

The undercoat coating film may further contain an anti-rust pigment, acoloring pigment, a metallic pigment, an extender pigment or the like.Examples of the anti-rust pigment include non-chromium-based anti-rustpigments such as modified silica, vanadates, magnesiumhydrogenphosphate, magnesium phosphate, zinc phosphate, aluminumpolyphosphate and the like, and chromium-based anti-rust pigments suchas strontium chromate, zinc chromate, barium chromate, calcium chromateand the like. Example of the coloring pigment include titanium oxide,carbon black, chromium oxide, iron oxide, colcothar, titanium yellow,cobalt blue, cobalt green, Aniline Black, and Phthalocyanine Blue.Example of the metallic pigment include aluminum flakes (non-leafingtype), bronze flakes, copper flakes, stainless steel flakes, and nickelflakes. Examples of the extender pigment include barium sulfate,titanium oxide, silica, and calcium carbonate.

The content of the pigment in the undercoat coating film can bedetermined as appropriate, as far as the effect of the presentembodiment can be achieved. For example, the content of the anti-rustpigment in the undercoat coating film is preferably, for example, 10 to70 vol %.

Also, the coated metal sheet further has an intercoat coating filmbetween the undercoat coating film and the overcoat coating film, fromthe viewpoint of improving the adhesiveness and the corrosion resistanceof the overcoat coating film in the coated metal sheet.

The intercoat coating film is composed of resin. Examples of the resininclude fluorine resin such as polyvinylidene fluoride and the like,polyester, polyester-modified silicones, acrylic resin, polyurethane,and polyvinyl chloride. The intercoat coating film also may furthercontain additives such as an anti-rust pigment, a coloring pigment, ametallic pigment, or the like, similarly as the undercoat coating film,as far as the effect of the present embodiment can be achieved.

The coated metal sheet according to the present embodiment is achromate-free or chromate-based coated metal sheet. “Chromate-free”means that the coated metal sheet contains substantially no hexavalentchromium. It is possible to confirm that the coated metal sheet is“chromate-free” as follows. For example, in any of the metal sheet, thechemical conversion film, the undercoat coating film, and the overcoatcoating film aforementioned, four 50 mm×50 mm specimens are cut off froma metal sheet on which the overcoat coating film or the undercoatcoating film has been produced singly, and the specimens are immersed in100 mL of boiling pure water for 10 minutes. Then, when hexavalentchromium eluted in pure water is quantified by a concentration analysismethod in compliance with JIS H8625, Annex 2. 4. 1, “DiphenylcarbazideVisual Colorimetric Method”, the concentration shall be lower than thedetection limit. Hexavalent chromium is not eluted form the coated metalsheet during actual use into the environment, and the coated metal sheetexhibits sufficient corrosion resistance at its flat portion.Incidentally, a “flat portion” refers to a portion that is covered withthe overcoat coating film of the metal sheet and has not been deformedby bending, drawing, bulging, embossing, roll-forming or the like.

The coated metal sheet is suitable for a matte-coated metal sheet. Matterefers to a glossiness at 60° being from 0.1 to 15. When the glossinessis extremely high, an enamel-like gloss may predominate, and a mattefeeing may not be achieved. The above-described glossiness is adjustedwith the average particle diameter of the gloss adjusting agent andmatting agent, their contents in the overcoat coating film and the like.

The coated metal sheet include a first step of applying an overcoatcoating material that contains the fluorine resin, the gloss adjustingagent, and the matting agent onto the metal sheet and a second step ofcuring the coating film of the overcoat coating material to form theovercoat coating film.

In the above-described first step, the overcoat coating material may beapplied directly onto the surface of the metal sheet, may be appliedonto the chemical conversion film formed on the surface of the metalsheet, or may be applied onto the undercoat coating film formed on thesurface of the coated metal sheet or the surface of the chemicalconversion film.

The overcoat coating material is prepared by, for example, dispersingthe materials for the overcoat coating film aforementioned in a solvent.The coating material may contain a solvent, a crosslinking agent and thelike. Examples of the solvent include hydrocarbons such as toluene,xylene and the like; esters such as ethyl acetate, butyl acetate and thelike; ethers such as cellosolve and the like; and ketones such as methylisobutyl ketone, methyl ethyl ketone, isophorone, cyclohexanone and thelike.

The overcoat coating material is applied, for example, by a known methodsuch as roll coating, curtain flow coating, spray coating, immersioncoating and the like. The amount of the overcoat coating material coatedis adjusted as appropriate, depending on the intended film thickness Tof the overcoat coating film.

Incidentally, as aforementioned, blending a matting agent into theovercoat coating film allows a unique design to be exhibited as well ascan improve the scratch resistance of the coated metal sheet. In orderto achieve both the designability and the scratch resistance, theovercoat coating film is preferably coated thicker than a coating filmthat contains a gloss adjusting agent only and contains no mattingagent. Also, since the ratio of nonvolatile ingredients in the coatingmaterial increases by blending a matting agent into the overcoat coatingfilm, the overcoat coating film can be coated thicker than a coatingfilm that contains a gloss adjusting agent only and contains no mattingagent.

The gloss adjusting agent contained in the overcoat coating materialsatisfies the aforementioned size conditions. In the overcoat coatingmaterial, when the gloss adjusting agent does not satisfy theaforementioned size conditions, the overcoat coating material thatsatisfies the above-described conditions can be obtained by subjectingthe overcoat coating material to treatment for pulverizing the particlesin the overcoat coating material. Examples of the above-described“treatment for pulverizing the particles” include roller mill treatment.More specifically, the treatment is conducted by appropriately settingthe clearance between the rollers of the roller mill and treatment timesuch that the Ru falls below 1.2T before a matting agent is blended tothe overcoat coating material. Thereafter, the overcoat coating materialthat satisfies the above-described conditions can be obtained byblending the matting agent.

The above-described second step can be conducted, for example, by aknown method for baking the overcoat coating material onto a metalsheet. For example, in the second step, a metal sheet to which aovercoat coating material has been applied is heated such that thetemperature of the metal sheet reaches 200 to 250° C.

The production method of the coated metal sheet may include other stepsother than the first step and second step aforementioned, as far as theeffect of the present invention can be achieved. Examples of the othersteps include a step for forming a chemical conversion film, a step forforming an undercoat coating film, and a step for forming an intercoatcoating film.

The chemical conversion film can be formed by applying an aqueouschemical conversion liquid for forming the film by a known method suchas roll-coating, spin-coating, spraying methods and the like, to themetal sheet surface and drying the metal sheet after application withoutwater washing. The drying temperature and the drying time for the metalsheet are preferably 60 to 150° C. as the temperature which the metalsheet reaches and 2 to 10 seconds, for example, from the viewpoint ofproductivity.

The undercoat coating film is produced by application of a coatingmaterial for undercoat coating films (undercoat coating material). Theundercoat coating material may contain a solvent, a crosslinking agentand the like. Examples of the solvent include compounds exemplified assolvents for the overcoat coating material. Examples of the crosslinkingagent include melamine resin, isocyanate resin and the like forcrosslinking the resin aforementioned. The undercoat coating material isprepared by homogeneously mixing and dispersing the materialsaforementioned.

The undercoat coating material is, for example, applied on the metalsheet by the known method aforementioned for overcoat coating materialsuch that a dry film thickness of 1 to 10 μm, preferably 3 to 7 μm isobtained. A coating film of the coating material is produced by heatinga metal sheet at, for example, 180 to 240° C., a temperature which themetal sheet achieves, thereby baking the film onto the metal sheet.

The intercoat coating film is also produced by application of a coatingmaterial for intercoat coating films (intercoat coating material),similarly as the undercoat coating film. The intercoat coating materialalso may contain the solvent, the crosslinking agent and the like inaddition to the materials for the intercoat coating film. The intercoatcoating material is prepared by homogeneously mixing and dispersing thematerials aforementioned. The intercoat coating material is preferablyapplied, for example, by the above-described known method, to theundercoat coating film in an amount to be coated such that the sum ofthe dry film thickness of the coating material and the film thickness ofthe undercoat coating film reaches 3 to 20 μm (preferably 5 to 15 μm),from the viewpoint of the processability. A coating film of the coatingmaterial is produced by heating a metal sheet at, for example, 180 to240° C., a temperature which the metal sheet achieves, thereby bakingthe film above the metal sheet.

Applications of the coated metal sheet are suitable for exterior use.“For exterior use” refers to being used in portions exposed to the openair such as roofs, walls, accessories, signboards, outdoor-installedapparatuses and the like, wherein the portions may be irradiated with asunbeam and its reflected light. Examples of the coated metal sheet forexterior use include coated metal sheets for exterior building materialsand the like.

The coated metal sheet is formed into an exterior building material byknown processing such as bending, drawing, bulging, embossing,roll-forming or the like. In this manner, the exterior building materialis composed of the coated metal sheet. The exterior building materialmay further include other structure as far as the above-describedeffects can be achieved. For example, the exterior building material mayfurther have a structure to be subjected to appropriate installationduring actual use of the exterior building material. Examples of such astructure include members to fix an exterior building material to abuilding, members to connect a plurality of exterior building materials,marks that show the direction of an exterior building material onmounting, foam sheets and foam layers to improve the thermal insulationproperties and the like. These structures may be included in the coatedmetal sheet for exterior use aforementioned.

In the coated metal sheet, the gloss adjusting agent (microporousparticles) is sufficiently confined in the overcoat coating film.Additionally, the particle diameter of the gloss adjusting agent in theovercoat coating film in the film thickness direction of the overcoatcoating film is likely to become sufficiently small as its particleshape is lower-profile. Furthermore, about 97.5% by number, that is, themost portion of the gloss adjusting agent has a sufficiently smallparticle diameter of 0.9T or less relative to the film thickness T ofthe overcoat coating film. Thus, the overcoat coating film can bedesigned such that the microporous particles are not exposed within theintended age of service, even if the resin in the overcoat coating filmis gradually worn from the surface of the overcoat coating film byactual use in an exterior application.

Meanwhile, in the coated metal sheet, although the matting agent iscovered with the resin constituting the overcoat coating film, at leasta part of the particles in the matting agent is larger than the filmthickness of a portion of the overcoat coating film where the mattingagent is not contained. Thus, the matting agent may appear from theovercoat coating film when the resin in the overcoat coating film isgradually worn from the surface of the overcoat coating film by actualuse in an exterior application, even during the intended age of service.In such a situation, if microporous particles as the matting agent arecontained in the overcoat coating film, a portion of the overcoatcoating film where the matting agent cracks, collapses, or falls off maybecome an origin of corrosion. Thus, primary particles are contained asthe matting agent in the coated metal sheet. Therefore, even if theprimary particles appear from the surface of the overcoat coating filmby actual use in an exterior application, cracking and collapse as thoseoccurring in microporous particles and fall-off from the overcoatcoating film are prevented, and corrosive factors such as rainwatercannot reach the metal sheet.

Therefore, cracking, collapse, and falling-off from the overcoat coatingfilm of the gloss adjusting agent (microporous particles) and cracking,collapse, and falling-off from the overcoat coating film of the mattingagent (primary particles) within the intended age of service areprevented, and corrosive factors such as rainwater and the like cannotreach the metal sheet during the intended age of service. Thus, thecoated metal sheet, if being chromate-free (if the metal sheet has beennon-chromate anti-rust treated), exhibits flat portion-corrosionresistance at least equivalent to that of conventional chromate-treatedcoated metal sheets, and if having been subjected to chromate treatment,exhibits flat portion-corrosion resistance equivalent to or greater thanthat of conventional chromate-treated coated metal sheets. Examples ofthe “chromate treatment” of the coated metal sheet in the embodimentinclude, in addition to the chromate anti-rust treatment of the metalsheet, the adoption of an undercoat coating film containing achromate-based anti-rust pigment. Examples of the “coated metal sheetsubjected to chromate treatment” include coated metal sheets that have anon-chromate anti-rust treated metal sheet and an undercoat coating filmcontaining a chromate-based anti-rust pigment, coated metal sheets thathas a chromate anti-rust treated metal sheet and an undercoat coatingfilm containing no chromate-based anti-rust pigment, and coated metalsheet that have a chromate anti-rust treated metal sheet and anundercoat coating film containing a chromate-based anti-rust pigment.

As clear from the above description, according to the presentembodiment, there can be provided a coated metal sheet which, even beingchromate-free, has sufficient flat-portion corrosion resistance, whereinthe coated metal sheet has a metal sheet and an overcoat coating filmdisposed on the metal sheet, wherein the overcoat coating film containsfluorine resin and a gloss adjusting agent which is particles havingmicropores (microporous particles) and a matting agent which is primaryparticles, wherein the content of the gloss adjusting agent in theovercoat coating film is from 0.01 to 15 vol %, and the content of thematting agent in the overcoat coating film is from 0.01 to 15 vol %, andwherein the following equations are satisfied:

D1_(97.5) /T≦0.9

Ru≦1.2T

R1≧1.0

0.5≦D2_(97.5) /T≦7.0

3≦T≦40

wherein R1 (μm) is the number average particle diameter of the glossadjusting agent, T (μm) is the film thickness of the overcoat coatingfilm, D1_(97.5) (μm) is the 97.5% particle diameter in the numberparticle size distribution of the gloss adjusting agent, D2_(97.5) (μm)is the 97.5% particle diameter in the accumulated particle sizedistribution of the matting agent based on the number of particles, andRu (μm) is the upper limit particle diameter in the number particle sizedistribution of the gloss adjusting agent.

The fact that the Ru is less than T is even more effective, from theviewpoint of further improvement of the flat portion-corrosionresistance of the coated metal sheet, or from the viewpoint of furtherprolongation of the life of the coated metal sheet having sufficientflat portion-corrosion resistance.

Additionally, the fact that the metal sheet has been subjected tonon-chromate anti-rust treatment and the coated metal sheet ischromate-free is even more effective, from the viewpoint of reducingenvironmental loads in use or production of the coated metal sheet, andthe fact that the metal sheet has been subjected to chromate anti-rusttreatment is even more effective, from the viewpoint of furtherimprovement of the flat portion-corrosion resistance of the coated metalsheet.

Also, the fact that the gloss adjusting agent is silica particles iseven more effective, from the viewpoint of inexpensively producingcoated metal sheets having the intended designability.

Also, the fact that the coated metal sheet further has an undercoatcoating film between the metal sheet and the overcoat coating film ismore effective from the viewpoint of improving the adhesiveness andcorrosion resistance of the overcoat coating film in the coated metalsheet, and the fact that the coated metal sheet further has an intercoatcoating film between the undercoat coating film and the overcoat coatingfilm is even more effective, from the above-described viewpoint.

Additionally, the fact that the overcoat coating film is composed of aresin component comprising polyvinylidene fluoride and acrylic resin asthe main component is even more effective, from the viewpoint that theproperties of the fluorine resin such as weather resistance, corrosionresistance, and contamination resistance and the properties of theacrylic resin such as adhesiveness of the overcoat coating film are bothexhibited.

Also, when the coated metal sheet has a glossiness at 60° of 0.1 to 15,both the intended designability and sufficient flat portion-corrosionresistance are achieved.

Additionally, the fact that the coated metal sheet is a coated metalsheet for exterior use is further effective from the viewpoint ofreducing a load on the environment due to elution of chromium duringactual use.

An exterior building material composed of the coated metal sheet ischromate-free as well as can exhibit excellent flat portion-corrosionresistance during actual use of 10 years or more.

Additionally, the aforementioned method for producing a coated metalsheet having the metal sheet and the overcoat coating film disposed onthe metal sheet comprises the steps of: applying an overcoat coatingmaterial that contains the fluorine resin, the gloss adjusting agent,and the matting agent onto the metal sheet and curing the coating filmof the overcoat coating material to form the overcoat coating film,wherein the content of the gloss adjusting agent in the overcoat coatingfilm is from 0.01 to 15 vol %, and the content of the matting agent inthe overcoat coating film is from 0.01 to 15 vol %, wherein the glossadjusting agent is particles having micropores, and the matting agent isprimary particles, and wherein the gloss adjusting agent and the mattingagent which satisfy the following equations are employed:

D1_(97.5) /T≦0.9

Ru≦1.2T

R1≧1.0

0.5≦D2_(97.5) /T≦7.0

3≦T≦40

wherein R1 (μm) is the number average particle diameter of the glossadjusting agent, T (μm) is the film thickness of the overcoat coatingfilm, D1_(97.5) (μm) is the 97.5% particle diameter in the numberparticle size distribution of the gloss adjusting agent, D2_(97.5) (μm)is the 97.5% particle diameter in the accumulated particle sizedistribution of the matting agent based on the number of particles, andRu (μm) is the upper limit particle diameter in the number particle sizedistribution of the gloss adjusting agent. Accordingly, it is possibleto provide a coated metal sheet which, even being chromate-free, hasexcellent flat-portion corrosion resistance equivalent to or greaterthan that of coated metal sheets comprising a chromate anti-rust treatedmetal sheet.

In the above-described production method, when the overcoat coatingmaterial has been subjected to treatment for pulverizing the particlesin the overcoat coating material, coarse particles present accidentallyand irregularly in the overcoat coating film are substantially removedfrom the overcoat coating material. Thus, the treatment is even moreeffective, from the viewpoint of further improvement of the flatportion-corrosion resistance of the coated metal sheet.

Hereinafter, the present invention will be described in more detail withreference to Examples, but the present invention is not limited by theseExamples.

EXAMPLES

[Production of Coated Base Sheets 1 to 5]

A hot-dip 55% Al—Zn alloy-plated steel sheet having an amount depositedon both the sides of 150 g/m² was alkali-degreased (base sheet 1).Subsequently, a non-chromate anti-rust treatment solution describedbelow at 20° C. was applied to the surface of the plated layer of theplated steel sheet, as pre-coating treatment. The plated steel sheet wasdried at 100° C. without washing with water to thereby obtain anon-chromate anti-rust treated plated steel sheet having an amount ofdeposited of 10 mg/m² in terms of Ti (base sheet 2).

(Non-Chromate Anti-Rust Treatment Solution)

Hexafluorotitanate 55 g/L Hexafluorozirconate 10 g/LAminomethyl-substituted 72 g/L polyvinyl phenol Water Balance

Additionally, to a surface of base sheet 2, the following undercoatcoating material containing epoxy resin was applied. The chemicalconversion steel sheet was heated such that the temperature of theplated steel sheet reached 200° C. to thereby obtain the chromate-freeplated steel sheet including an undercoat coating film having a dry filmthickness of 5 μm (base sheet 3).

Phosphate mixture 15 vol % Barium sulfate 5 vol % Silica 1 vol % Clearcoating material Balance

Alternatively “SURFCOAT NRC300NS” manufactured by Nippon Paint Co., Ltd.(“SURFCOAT” is a registered trademark of the company), which is achromate treatment solution, was used instead of the chromate-freetreatment solution to conduct chromate anti-rust treatment of an amountdeposited of 20 mg/m² in terms of chromium. Subsequently, to the surfaceof the chromate anti-rust treated plated steel sheet, the followingundercoat coating material containing epoxy resin was applied. Thechemical conversion steel sheet was heated such that the temperature ofthe plated steel sheet reached 200° C. to thereby obtain a plated steelsheet including a chromate-based undercoat coating film having a dryfilm thickness of 5 μm (base sheet 4).

Strontium chromate 15 vol % Barium sulfate 5 vol % Silica 1 vol % Clearcoating material Balance

Incidentally, in the undercoat coating material, the clear coatingmaterial is “NSC680” manufactured by Nippon Fine Coatings Co., Ltd. Inthe undercoat coating material, the phosphate mixture is a mixture ofmagnesium hydrogenphosphate, magnesium phosphate, zinc phosphate, andaluminum tripolyphosphate. Also, the silica is a extender pigment andhas an average particle diameter of 5 μm. Additionally, the vol % is aproportion relative to the solid content in the undercoat coatingmaterial.

Alternatively, to a surface of base sheet 3, the following intercoatcoating material containing polyester was applied. The chemicalconversion steel sheet was heated such that the temperature of theplated steel sheet reached 220° C. to thereby obtain the chromate-freeplated steel sheet including an intercoat coating film having a dry filmthickness of 15 μm on the undercoat coating film (base sheet 5).

Carbon black 7 vol % Silica particles 1 1 vol % Fluorine resin-basedBalance coating material

The fluorine resin-based coating material is a clear coating material“DICFLUOR C” manufactured by Nippon Fine Coatings Inc., which is afluorine resin (PVDF/AR)-based coating material. Carbon black is acoloring pigment. The vol % described above is a proportion relative tothe solid content in the intercoat coating material.

Also, silica particles 1 described above (silica 1) are a classifiedmaterial or its mixture, for example, and have a particle sizedistribution like the normal distribution. The number average particlediameter R1 of the silica particles 1 is 7.0 μm, and D1_(97.5) in thenumber particle size distribution is 22.0 μm. Additionally, the upperlimit particle diameter Ru in the number particle size distribution is23.5 μm.

The following ingredients were mixed in the following amounts to therebyobtain an overcoat coating material.

Carbon black 7 vol % Silica particles 1 5 vol % Acrylic particles 1 5vol % Clear coating material 1 Balance

The clear coating material 1 described above is “DICFLUOR C”manufactured by Nippon Fine Coatings Co., Ltd., which is a fluorineresin (PVDF/AR)-based coating material. Carbon black is a coloringpigment. The vol % described below is a proportion relative to the solidcontent in the overcoat coating material.

Acrylic particles 1 described above (acrylic 1) have a particle sizedistribution like the normal distribution. Acrylic particles 1, whichhave been produced by suspension polymerization, correspond to theaforementioned primary particles. The number average particle diameterR2 of acrylic particles 1 is 35 μm, and D2_(97.5) in the number particlesize distribution is 50 μm.

[Production of Coated Metal Sheet 1]

The overcoat coating material was applied to the surface of theundercoat coating film of base sheet 3. Base sheet 3 was heated suchthat the temperature of the plated steel sheet in base sheet 3 reached220° C. to thereby produce an overcoat coating film having a dry filmthickness T of 25 μm. Coated metal sheet 1 was thus produced.

Incidentally, coated metal sheet 1 was cut to allow its cross section tobe exposed. The cross section was encapsulated inside a mass of epoxyresin, further ground, and photographed with a scanning electronmicroscope. The resulting images of a plurality of spots were processedand analyzed to determine the particle size distribution of silicaparticles 1 and acrylic particles 1. R1, R2, D1_(97.5), D2_(97.5), andRu were confirmed to be substantially equivalent to the numericalvalues.

[Production of Coated Metal Sheets 2 and 3]

Coated metal sheet 2 was produced in the same manner as coated metalsheet 1 except that the amount of the overcoat coating materialdeposited was changed such that the dry film thickness T reached 22 μm.Additionally, coated metal sheet 3 was produced in the same manner ascoated metal sheet 1 except that the amount of the overcoat coatingmaterial deposited was changed such that the dry film thickness Treached 20 μm.

[Production of Coated Metal Sheet 4]

Coated metal sheet 4 was produced in the same manner as coated metalsheet 1 except that silica particles 2 were used instead of silicaparticles 1 as the gloss adjusting agent in the overcoat coatingmaterial, acrylic particles 2 were used instead of acrylic particles 1as the matting agent, and the amount of the overcoat coating materialcoated was changed such that the dry film thickness T reached 3 μm.Silica particles 2 are a classified material or its mixture, forexample, wherein R1 is 1.0 μm, D1_(97.5) is 2.0 μm, and Ru is 2.6 μm.The number average particle diameter R2 of acrylic particles 2 is 10 μm,and D2_(97.5) in the number particle size distribution is 15 μm.

[Production of Coated Metal Sheet 5]

Coated metal sheet 5 was produced in the same manner as coated metalsheet 4 except that the amount of the overcoat coating material coatedwas changed such that the dry film thickness T reached 2 μm.

[Production of Coated Metal Sheets 6 and 7]

Coated metal sheet 6 was produced in the same manner as coated metalsheet 1 except that silica particles 3 were used instead of silicaparticles 1 as the gloss adjusting agent in the overcoat coatingmaterial, and the amount of the overcoat coating material coated waschanged such that the dry film thickness T reached 40 μm. Silicaparticles 3 are a classified material or its mixture, for example,wherein R1 is 5.0 μm, D1_(97.5) is 7.6 μm, and Ru is 9.5 μm.Additionally, coated metal sheet 7 was produced in the same manner ascoated metal sheet 6 except that the amount of the overcoat coatingmaterial coated was changed such that the dry film thickness T reached41 μm.

[Production of Coated Metal Sheets 8 to 11]

Coated metal sheet 8 was produced in the same manner as coated metalsheet 1 except that silica particles 4 were used instead of silicaparticles 1 as the gloss adjusting agent in the overcoat coatingmaterial. Silica particles 4 are a classified material or its mixture,for example, wherein R1 is 8.2 μm, D1_(97.5) is 22.0 μm, and Ru is 31.3μm.

Additionally, coated metal sheet 9 was produced in the same manner ascoated metal sheet 1 except that silica particles 5 were used instead ofsilica particles 1 as the gloss adjusting agent in the overcoat coatingmaterial. Silica particles 5 are a classified material or its mixture,for example, wherein R1 is 8.5 μm, D1_(97.5) is 22.8 μm, and Ru is 28.0μm.

Additionally, coated metal sheet 10 was produced in the same manner ascoated metal sheet 1 except that silica particles 6 were used instead ofsilica particles 1 as the gloss adjusting agent in the overcoat coatingmaterial. Silica particles 6 are a classified material or its mixture,for example, wherein R1 is 3.7 μm, D1_(97.5) is 5.4 μm, and Ru is 7.0μm.

Additionally, coated metal sheet 11 was produced in the same manner ascoated metal sheet 1 except that silica particles 7 were used instead ofsilica particles 1 as the gloss adjusting agent in the overcoat coatingmaterial. Silica particles 7 are a classified material or its mixture,for example, wherein R1 is 0.7 μm, D1_(97.5) is 1.4 μm, and Ru is 2.0μm.

[Production of Coated Metal Sheet 12]

Coated metal sheet 12 was produced in the same manner as coated metalsheet 1 except that silica particles 8 were used instead of silicaparticles 1 as the gloss adjusting agent in the overcoat coatingmaterial, and the content of the silica particles in the overcoatcoating material was changed to 0.0005 vol %. Silica particles 8 are aclassified material or its mixture, for example, wherein R1 is 7.0 μm,D1_(97.5) is 12.3 μm, and Ru is 20.0 μm.

[Production of Coated Metal Sheets 13 to 18]

Coated metal sheet 13 was produced in the same manner as coated metalsheet 12 except that the content of the silica particles in the overcoatcoating material was changed to 0.01 vol %. Additionally, coated metalsheet 14 was produced in the same manner as coated metal sheet 12 exceptthat the content of the silica particles in the overcoat coatingmaterial was changed to 0.1 vol %. Additionally, coated metal sheet 15was produced in the same manner as coated metal sheet 12 except that thecontent of the silica particles in the overcoat coating material waschanged to 5 vol %. Additionally, coated metal sheet 16 was produced inthe same manner as coated metal sheet 12 except that the content of thesilica particles in the overcoat coating material was changed to 15 vol%. Additionally, coated metal sheet 17 was produced in the same manneras coated metal sheet 12 except that the content of the silica particlesin the overcoat coating material was changed to 16 vol %. Furthermore,coated metal sheet 18 was produced in the same manner as coated metalsheet 12 except that the content of the silica particles in the overcoatcoating material was changed to 20 vol %.

[Production of Coated Metal Sheets 19 to 24]

Coated metal sheet 19 was produced in the same manner as coated metalsheet 15 except that acrylic particles 3 were used instead of acrylicparticles 1 as the matting agent in the overcoat coating material.Acrylic particles 3, which have been produced by suspensionpolymerization, correspond to the aforementioned primary particles. Inacrylic particles 3, R2 is 8.0 μm, and D2_(97.5) is 12.0 μm.

Additionally, coated metal sheet 20 was produced in the same manner ascoated metal sheet 15 except that acrylic particles 4 were used insteadof acrylic particles 1 as the matting agent in the overcoat coatingmaterial. Acrylic particles 4, which have been produced by suspensionpolymerization, correspond to the aforementioned primary particles. Inacrylic particles 4, R2 is 7.0 μm, and D2_(97.5) is 12.5 μm.

Additionally, coated metal sheet 21 was produced in the same manner ascoated metal sheet 15 except that acrylic particles 5 were used insteadof acrylic particles 1 as the matting agent in the overcoat coatingmaterial. Acrylic particles 5, which have been produced by suspensionpolymerization, correspond to the aforementioned primary particles. Inacrylic particles 5, R2 is 18.0 μm, and D2_(97.5) is 25.0 μm.

Additionally, coated metal sheet 22 was produced in the same manner ascoated metal sheet 15 except that acrylic particles 6 were used insteadof acrylic particles 1 as the matting agent in the overcoat coatingmaterial. Acrylic particles 6, which have been produced by suspensionpolymerization, correspond to the aforementioned primary particles. Inacrylic particles 6, R2 is 80.0 μm, and D2_(97.5) is 120.0 μm.

Additionally, coated metal sheet 23 was produced in the same manner ascoated metal sheet 15 except that acrylic particles 7 were used insteadof acrylic particles 1 as the matting agent in the overcoat coatingmaterial. Acrylic particles 7, which have been produced by suspensionpolymerization, correspond to the aforementioned primary particles. Inacrylic particles 7, R2 is 120.0 μm, and D2_(97.5) is 200.0 μm.

Additionally, coated metal sheet 24 was produced in the same manner ascoated metal sheet 15 except that polyacrylonitrile (PAN) particles 1were used instead of acrylic particles 1 as the matting agent in theovercoat coating material. PAN particles 1, which have been produced bya spray dry method, correspond to the aforementioned microporousparticles. R2 is 23.0 μm, D2_(97.5) is 55.0 μm.

[Production of Coated Metal Sheets 25 to 31]

Coated metal sheet 25 was produced in the same manner as coated metalsheet 15 except that the content of the acrylic particles in theovercoat coating material was changed to 0.0005 vol %. Additionally,coated metal sheet 26 was produced in the same manner as coated metalsheet 15 except that the content of the acrylic particles in theovercoat coating material was changed to 0.01 vol %. Additionally,Coated metal sheet 27 was produced in the same manner as coated metalsheet 15 except that the content of the acrylic particles in theovercoat coating material was changed to 0.1 vol %. Additionally, coatedmetal sheet 28 was produced in the same manner as coated metal sheet 15except that the content of the acrylic particles in the overcoat coatingmaterial was changed to 13.0 vol %. Additionally, coated metal sheet 29was produced in the same manner as coated metal sheet 15 except that thecontent of the acrylic particles in the overcoat coating material waschanged to 15.0 vol %. Additionally, coated metal sheet 30 was producedin the same manner as coated metal sheet 15 except that the content ofthe acrylic particles in the overcoat coating material was changed to16.0 vol %. Furthermore, coated metal sheet 31 was produced in the samemanner as coated metal sheet 15 except that the content of the acrylicparticles in the overcoat coating material was changed to 20.0 vol %.

[Production of Coated Metal Sheets 32 to 34]

Coated metal sheet 32 was produced in the same manner as coated metalsheet 15 except that the overcoat coating film was formed on base sheet1 instead of on base sheet 3. Additionally, coated metal sheet 33 wasproduced in the same manner as coated metal sheet 15 except that theovercoat coating film was formed on base sheet 2 instead of on basesheet 3. Additionally, coated metal sheet 34 was produced in the samemanner as coated metal sheet 15 except that the overcoat coating filmwas formed on base sheet 4 instead of on base sheet 3.

[Production of Coated Metal Sheets 35 to 39]

Coated metal sheet 35 was produced in the same manner as coated metalsheet 34 except that silica particles 9 were used instead of silicaparticles 1 as the gloss adjusting agent in the overcoat coatingmaterial. Silica particles 9 are a classified material or its mixture,for example, wherein R1 is 7.0 μm, D1_(97.5) is 12.7 μm, and Ru is 23.3μm.

Coated metal sheet 36 was produced in the same manner as coated metalsheet 34 except that silica particles 10 were used instead of silicaparticles 1 as the gloss adjusting agent in the overcoat coatingmaterial. Silica particles 10 are a classified material or its mixture,for example, wherein R1 is 8.0 μm, D1_(97.5) is 15.3 μm, and Ru is 24.7μm.

Coated metal sheet 37 was produced in the same manner as coated metalsheet 15 except that silica particles 11 were used instead of silicaparticles 1 as the gloss adjusting agent in the overcoat coatingmaterial. Silica particles 11 are a classified material or its mixture,for example, wherein R1 is 5.0 μm, D1_(97.5) is 10.2 μm, and Ru is 20.0μm.

Coated metal sheet 38 was produced in the same manner as coated metalsheet 15 except that polyacrylonitrile (PAN) particles 2 were usedinstead of silica particles 1 as the gloss adjusting agent in theovercoat coating material. PAN particles 2 are a classified material orits mixture, for example, wherein R1 is 5.0 μm, D1_(97.5) is 12.7 μm,and Ru is 15.8 μm.

Coated metal sheet 39 was produced in the same manner as coated metalsheet 15 except that calcium carbonate-calcium phosphate composite(CaCPC) particles were used as the gloss adjusting agent in the overcoatcoating material instead of silica particles 15. The CaCPC particles area classified material or its mixture, for example, wherein R1 is 5.0 μm,D1_(97.5) is 12.7 μm, and Ru is 15.8 μm.

[Production of Coated Metal Sheet 40]

Coated metal sheet 40 was produced in the same manner as coated metalsheet 37 except that glass particles were used instead of acrylicparticles 1 as the matting agent in the overcoat coating material. Theglass particles correspond to the aforementioned primary particles. Inthe glass particles, R2 is 20.0 μm, and D2_(97.5) is 30.0 μm.

[Production of Coated Metal Sheet 41]

Coated metal sheet 41 was produced in the same manner as coated metalsheet 1 except that the overcoat coating film was formed on base sheet 5instead of on base sheet 3, the amount of the overcoat coating materialcoated was changed such that the dry film thickness T reached 10 μm, andsilica particles 12 were used instead of silica particles 1 as the glossadjusting agent in the overcoat coating material. Silica particles 12are a classified material or its mixture, for example, wherein R1 is 3.0μm, D1_(97.5) is 6.1 μm, and Ru is 12.0 μm.

[Evaluation]

Coated metal sheets 1 to 41 were each subjected to the measurement andtest described below.

(1) 60° Glossiness (G60)

The specular glossiness at 60° (G60), specified by JISK5600-4-7(ISO2813: 1994), of each of coated metal sheets 1 to 41 was measuredwith Gloss meter VG-2000 manufactured by NIPPON DENSHOKU INDUSTRIES CO.,LTD.

(2) Coating Appearance

The appearance of the overcoat coating film of each of coated metalsheets 1 to 41 after drying was evaluated in accordance with thefollowing criteria.

(Evaluation Criteria)

G: No abnormal glossiness and coating film defects are observed, thecoating film is flat, and a matte appearance is observed.NG1: The gloss is extremely high, and no matte appearance is obtained(the glossiness is higher than 15).NG2: Concealability is lacking.

(3) Scratch Resistance

Clemens-type scratch test was conducted each on coated metal sheets 1 to41 by using a diamond needle having a diameter of 125 μm and applying aload of 400 g, and evaluation was made in accordance with the followingcriteria.

(Evaluation Criteria)

G: No scratch reaching the base material (metal sheet) is observed.NG: Scratches reaching the base material (metal sheet) are observed.

(4) Processed Part Adhesiveness

Coated metal sheets 1 to 41 after 24 hours elapsed since theirproduction were each subjected to 2T bending (adhesion bending), and the2T bended portion was subjected to cellophane tape-peeling test andevaluated in accordance with the following criteria on the basis of thearea ratio (%) of the peeled portion to the portion subjected to thetest in the overcoat coating film.

(Evaluation Criteria)

A: No crack in the coating film is observed (0%).B: 3% or less of cracks in the coating filmC: 5% or less of cracks in the coating filmNG: More than 5% of peeling in the coating film is observed.

(5) Flat Portion-Corrosion Resistance

First, coated metal sheets 1 to 41 were each subjected to the xenon lampmethod-accelerated weathering test specified by JIS K5600-7-7 (ISO11341:2004) for 1,000 hours. Then, each sheet was subjected to the “neutralsalt water spray cycle test” specified by JIS H8502 (so-called JASOmethod) for 720 hours. The above-described two tests were conducted asone cycle. Test products subjected to one cycle (corresponding to aboutfive-year service life in actual use) and test products subjected to twocycles (corresponding to about 10-year service life) each for coatedmetal sheets 1 to 41 were washed with water. After observed for thepresence or absence of coating film blistering at the flat portion ofthe coated metal sheet by visual observation and magnified observationwith a loupe having a magnification of 10, the sheets were evaluated inaccordance with the following criteria. A or B would have no practicalproblem in use.

(Evaluation Criteria)

A: No blistering is observed.B: Slightly subtle blistering is observed by magnified observation, butno blistering is visually observed.C: Blistering is visually observed.

The base sheet type, the gloss adjusting agent type, the matting agenttype, R1, R2, D1_(97.5), D2_(97.5), Ru, T, the content of the glossadjusting agent, the content of the matting agent, the value ofD1_(97.5)/T, the value of D2_(97.5)/T, the value of Ru/T, andExample/Comparative Example of coated metal sheets 1 to 41 are shown inTable 1 and Table 2. The evaluation results of coated metal sheets 1 to41 are also shown in Table 3 and Table 4.

TABLE 1 Gloss adjusting agent Matting agent Over- Con- Con- Primary coattent tent particles/ Base T R1 D1_(97.5) Ru (vol D1_(97.5)/ R2 D2_(97.5)(vol D2_(97.5)/ Microporous No. sheet (μm) Type (μm) (μm) (μm) %) T Ru/TType (μm) (μm) %) T particles Category 1 3 25 Silica 7 22 23.5  5 0.880.9 Acrylic 35 50 5 2.0 Primary Example 1 1 particles 2 3 22 Silica 7 2223.5  5 1.0 1.1 Acrylic 35 50 5 2.3 Primary Comparative 1 1 particlesExample 3 3 20 Silica 7 22 23.5  5 1.1 1.18 Acrylic 35 50 5 2.5 PrimaryComparative 1 1 particles Example 4 3 3 Silica 1 2 2.6  5 0.7 0.9Acrylic 10 15 5 5.0 Primary Example 2 2 particles 5 3 2 Silica 1 2 2.6 5 1.0 1.3 Acrylic 10 15 5 7.5 Primary Comparative 2 2 particles Example6 3 40 Silica 5 7.6 9.5  5 0.2 0.2 Acrylic 35 50 5 1.3 Primary Example 31 particles 7 3 41 Silica 5 7.6 9.5  5 0.2 0.2 Acrylic 35 50 5 1.2Primary Comparative 3 1 particles Example 8 3 25 Silica 8.2 22 31.3  50.88 1.25 Acrylic 35 50 5 2.0 Primary Comparative 4 1 particles Example9 3 25 Silica 8.5 22.8 28  5 0.91 1.1 Acrylic 35 50 5 2.0 PrimaryComparative 5 1 particles Example 10 3 25 Silica 3.7 5.4 7  5 0.2 0.3Acrylic 35 50 5 2.0 Primary Example 6 1 particles 11 3 25 Silica 0.7 1.42  5 0.1 0.1 Acrylic 35 50 5 2.0 Primary Comparative 7 1 particlesExample 12 3 25 Silica 7 12.3 20  0.0005 0.5 0.8 Acrylic 35 50 5 2.0Primary Comparative 8 1 particles Example 13 3 25 Silica 7 12.3 20  0.010.5 0.8 Acrylic 35 50 5 2.0 Primary Example 8 1 particles 14 3 25 Silica7 12.3 20  0.1 0.5 0.8 Acrylic 35 50 5 2.0 Primary Example 8 1 particles15 3 25 Silica 7 12.3 20  5 0.5 0.8 Acrylic 35 50 5 2.0 Primary Example8 1 particles 16 3 25 Silica 7 12.3 20 15 0.5 0.8 Acrylic 35 50 5 2.0Primary Example 8 1 particles 17 3 25 Silica 7 12.3 20 16 0.5 0.8Acrylic 35 50 5 2.0 Primary Comparative 8 1 particles Example 18 3 25Silica 7 12.3 20 20 0.5 0.8 Acrylic 35 50 5 2.0 Primary Comparative 8 1particles Example 19 3 25 Silica 7 12.3 20  5 0.5 0.8 Acrylic 8 12 50.48 Primary Comparative 8 3 particles Example 20 3 25 Silica 7 12.3 20 5 0.5 0.8 Acrylic 7 12.5 5 0.5 Primary Example 8 4 particles 21 3 25Silica 7 12.3 20  5 0.5 0.8 Acrylic 18 25 5 1.0 Primary Example 8 5particles 22 3 25 Silica 7 12.3 20  5 0.5 0.8 Acrylic 80 120 5 4.8Primary Example 8 6 particles

TABLE 2 Matting agent Gloss adjusting agent Primary Over- Con- Con-particles/ coat tent tent Micro- Base T R1 D1_(97.5) Ru (vol D1_(97.5)/R2 D2_(97.5) (vol D2_(97.5)/ porous No. sheet (μm) Type (μm) (μm) (μm)%) T Ru/T Type (μm) (μm) %) T particles Category 23 3 25 Silica 8 7 12.320 5 0.5 0.8 Acrylic 120 200  5 8.0 Primary Comparative 7 particlesExample 24 3 25 Silica 8 7 12.3 20 5 0.5 0.8 PAN1 23 55  5 2.2 Micro-Comparative porous Example particles 25 3 25 Silica 8 7 12.3 20 5 0.50.8 Acrylic 35 50  0.0005 2.0 Primary Comparative 1 particles Example 263 25 Silica 8 7 12.3 20 5 0.5 0.8 Acrylic 35 50  0.01 2.0 PrimaryExample 1 particles 27 3 25 Silica 8 7 12.3 20 5 0.5 0.8 Acrylic 35 50 0.1 2.0 Primary Example 1 particles 28 3 25 Silica 8 7 12.3 20 5 0.50.8 Acrylic 35 50 13 2.0 Primary Example 1 particles 29 3 25 Silica 8 712.3 20 5 0.5 0.8 Acrylic 35 50 15 2.0 Primary Example 1 particles 30 325 Silica 8 7 12.3 20 5 0.5 0.8 Acrylic 35 50 16 2.0 Primary Comparative1 particles Example 31 3 25 Silica 8 7 12.3 20 5 0.5 0.8 Acrylic 35 5020 2.0 Primary Comparative 1 particles Example 32 1 25 Silica 8 7 12.320 5 0.5 0.8 Acrylic 35 50  5 2.0 Primary Example 1 particles 33 2 25Silica 8 7 12.3 20 5 0.5 0.8 Acrylic 35 50  5 2.0 Primary Example 1particles 34 4 25 Silica 8 7 12.3 20 5 0.5 0.8 Acrylic 35 50  5 2.0Primary Example 1 particles 35 4 25 Silica 9 7 12.7 23.3 5 0.5 0.9Acrylic 35 50  5 2.0 Primary Example 1 particles 36 4 25 Silica 10 815.3 24.7 5 0.6 1.0 Acrylic 35 50  5 2.0 Primary Example 1 particles 373 25 Silica 11 5 10.2 20 5 0.4 0.8 Acrylic 35 50  5 2.0 Primary Example1 particles 38 3 25 PAN2 5 12.7 15.8 5 0.5 0.6 Acrylic 35 50  5 2.0Primary Example 1 particles 39 3 25 CaCPC 5 12.7 15.8 5 0.5 0.6 Acrylic35 50  5 2.0 Primary Example 1 particles 40 3 25 Silica 11 5 10.2 20 50.4 0.8 Glass 20 30  5 1.2 Primary Example particles 41 5 10 Silica 12 3 6.1 12 5 0.6 1.20 Acrylic 35 50  5 5.0 Primary Example 1 particles

TABLE 3 Processed Flat-portion corrosion Coating Scratch part resistanceNo. G60 appearance resistance adhesiveness 1 cycle 2 cycles Category 110 G G C A A Example 2 9 G G C B C Comparative Example 3 8 G G C B CComparative Example 4 13 G G B A A Example 5 5 NG2 NG C — — ComparativeExample 6 15 G G A A A Example 7 16 NG1 G A — Comparative Example 8 5 GG C B C Comparative Example 9 6 G G C B C Comparative Example 10 15 G GA A A Example 11 16 NG1 G A — Comparative Example 12 16 NG1 G A — —Comparative Example 13 15 G G A A A Example 14 15 G G A A A Example 15 8G G A A A Example 16 2 G G A A B Example 17 1 G G NG — — ComparativeExample 18 0.2 G G NG — — Comparative Example 19 12 G NG A — —Comparative Example 20 12 G G A A A Example 21 8 G G A A A Example 22 4G G A A A Example

TABLE 4 Processed Flat-portion corrosion Coating Scratch part resistanceNo. G60 appearance resistance adhesiveness 1 cycle 2 cycles Category 232 G G NG — — Comparative Example 24 8 G G A B C Comparative Example 2518 NG1 NG A — — Comparative Example 26 15 G G A A A Example 27 12 G G AA A Example 28 5 G G A A A Example 29 3 G G A A A Example 30 1 G G NG —— Comparative Example 31 0.4 G G NG — — Comparative Example 32 8 G G A BB Example 33 8 G G A A B Example 34 8 G G A A A Example 35 8 G G A A AExample 36 7 G G B A A Example 37 8 G G A A A Example 38 8 G G A A AExample 39 8 G G A A A Example 40 8 G G A A A Example 41 5 G G B A AExample

(6) Flat Portion-Corrosion Resistance

Coated metal sheets 15, 34, 35, and 36 were each subjected to up tothree cycles of the aforementioned test according to flatportion-corrosion resistance (corresponding to about 15-year servicelife in actual use), and test products subjected to three cycles wereeach washed with water. After observed for the presence or absence ofcoating film blistering at the flat portion of the coated metal sheet byvisual observation and magnified observation with a loupe having amagnification of 10, the sheets were evaluated in accordance with theaforementioned criteria. The results are shown in Table 5.

TABLE 5 Flat-portion Coated metal corrosion resistance sheet No. 1 cycle2 cycles 3 cycles Category 15 A A B Example 34 A A A Example 35 A A AExample 36 A A A Example

Reference Experiment 1

Particles having a particle diameter R1′ of 0.7T μm (T=25 μm) or morewere removed from silica particles 1 to obtain silica particles 1substantially containing no particles of 17.5 μm or more. Theseparticles are referred to as silica particles 13. Then, coated metalsheet 42 was produced in the same manner as coated metal sheet 1 exceptthat silica particles 13 were used instead of silica particles 1 as thegloss adjusting agent in the overcoat coating material.

Additionally, particles having a particle diameter R1′ of 0.8T μm (20.0μm) or more were removed to separately provide silica particles Asubstantially containing no particles of 20.0 μm or more. Into 97.5parts by volume of silica particles 13, 2.5 parts by volume of silicaparticles A was mixed to obtain silica particles composed of 97.5 partsby volume of silica particles 13 of 0.7T or less and 2.5 parts by volumeof silica particles A of 0.8T or less (content ratio: 97.5/2.5). Theseparticles are referred to as silica particles 14. Then, coated metalsheet 43 was produced in the same manner as coated metal sheet 1 exceptthat silica particles 14 were used instead of silica particles 1 as thegloss adjusting agent in the overcoat coating material.

Additionally, particles having a particle diameter R1′ of 0.9T μm (22.5μm) or more were removed to separately provide silica particles Bsubstantially containing no particles of 22.5 μm or more. Into 97.5parts by volume of silica particles 13, 2.5 parts by volume of silicaparticles B was mixed to obtain silica particles composed of 97.5 partsby volume of silica particles 13 of 0.7T or less and 2.5 parts by volumeof silica particles B of 0.9T or less. These particles are referred toas silica particles 15. Then, coated metal sheet 44 was produced in thesame manner as coated metal sheet 1 except that silica particles 15 wereused instead of silica particles 1 as the gloss adjusting agent in theovercoat coating material.

Additionally, particles having a particle diameter R1′ of 1.0T μm (25.0μm) or more were removed to separately provide silica particles Csubstantially containing no particles of 25.0 μm or more. Into 97.5parts by volume of silica particles 13, 2.5 parts by volume of silicaparticles C was mixed to obtain silica particles composed of 97.5 partsby volume of silica particles 13 of 0.7T or less and 2.5 parts by volumeof silica particles C of 1.0T or less. These particles are referred toas silica particles 16. Then, coated metal sheet 45 was produced in thesame manner as coated metal sheet 1 except that silica particles 16 wereused instead of silica particles 1 as the gloss adjusting agent in theovercoat coating material.

Additionally, particles having a particle diameter R1′ of 1.1T μm (27.5μm) or more were removed to separately provide silica particles Dsubstantially containing no particles of 27.5 μm or more. Into 97.5parts by volume of silica particles 13, 2.5 parts by volume of silicaparticles D was mixed to obtain silica particles composed of 97.5 partsby volume of silica particles 13 of 0.7T or less and 2.5 parts by volumeof silica particles D of 1.1T or less. These particles are referred toas silica particles 17. Then, coated metal sheet 46 was produced in thesame manner as coated metal sheet 1 except that silica particles 17 wereused instead of silica particles 1 as the gloss adjusting agent in theovercoat coating material.

Additionally, particles having a particle diameter R1′ of 1.2T μm (30.0μm) or more were removed to separately provide silica particles Esubstantially containing no particles of 30.0 μm or more. Into 97.5parts by volume of silica particles 13, 2.5 parts by volume of silicaparticles E was mixed to obtain silica particles composed of 97.5 partsby volume of silica particles 13 of 0.7T or less and 2.5 parts by volumeof silica particles E of 1.2T or less. These particles are referred toas silica particles 18. Then, coated metal sheet 47 was produced in thesame manner as coated metal sheet 1 except that silica particles 18 wereused instead of silica particles 1 as the gloss adjusting agent in theovercoat coating material.

Additionally, particles having a particle diameter R1′ of 1.3T μm (32.5μm) or more were removed to separately provide silica particles Fsubstantially containing no particles of 32.5 μm or more. Into 97.5parts by volume of silica particles 13, 2.5 parts by volume of silicaparticles F was mixed to obtain silica particles composed of 97.5 partsby volume of silica particles 13 of 0.7T or less and 2.5 parts by volumeof silica particles F of 1.3T or less. These particles are referred toas silica particles 19. Then, coated metal sheet 48 was produced in thesame manner as coated metal sheet 1 except that silica particles 19 wereused instead of silica particles 1 as the gloss adjusting agent in theovercoat coating material.

Coated metal sheets 42 to 48 were evaluated for flat portion-corrosionresistance in accordance with the aforementioned method. The base sheettype, the gloss adjusting agent type, the matting agent type, R1, R2,D1_(97.5), D2_(97.5), the cut value, the particle diameter R1′ of themain component of the silica particles added, T, the content of thegloss adjusting agent, the content of the matting agent, the contentratio of two types of silica particles, and evaluation results of flatportion-corrosion resistance of coated metal sheets 42 to 48 are shownin Table 6.

TABLE 6 Gloss adjusting agent Matting agent Flat portion- Over- Con-Con- Primary corrosion coat Cut tent Con- tent particles/ resistanceBase T R1 D1_(97.5) value (vol tent R2 D2_(97.5) (vol D2_(97.5)/Microporous 1 2 No. sheet (μm) Type (μm) (μm) (μm) R1′ %) ratio Type(μm) (μm) %) T particles cycle cycles 42 3 25 Silica 7 22 23.5 — 5  100/Acrylic 35 50 5 2.0 Primary A A 13 0 1 particles 43 3 25 Silica 7 2223.5 20.0 5 97.5/ Acrylic 35 50 5 2.0 Primary A A 14 2. 5 1 particles 443 25 Silica 7 22 23.5 22.5 5 97.5/ Acrylic 35 50 5 2.0 Primary A A 152.5 1 particles 45 3 25 Silica 7 22 23.5 25.0 5 97.5/ Acrylic 35 50 52.0 Primary A B 16 2.5 1 particles 46 3 25 Silica 7 22 23.5 27.5 5 97.5/Acrylic 35 50 5 2.0 Primary B B 17 2.5 1 particles 47 3 25 Silica 7 2223.5 30.0 5 97.5/ Acrylic 35 50 5 2.0 Primary B B 18 2.5 1 particles 483 25 Silica 7 22 23.5 32.5 5 97.5/ Acrylic 35 50 5 2.0 Primary B C 192.5 1 particles

Reference Experiment 2

Silica particles composed of 97.0 parts by volume of silica particles 8of 0.7T or less and 3.0 parts by volume of silica particles E of 1.2T orless were obtained by changing the content ratio between silicaparticles 13 and silica particles E in silica particles 18. Theseparticles are referred to as silica particles 20. Then, coated metalsheet 49 was produced in the same manner as coated metal sheet 1 exceptthat silica particles 20 were used instead of silica particles 1 as thegloss adjusting agent in the overcoat coating material.

Additionally, silica particles composed of 96.5 parts by volume ofsilica particles 8 of 0.7T or less and 3.5 parts by volume of silicaparticles E of 1.2T or less were obtained by changing the content ratiobetween silica particles 13 and silica particles E in silica particles18. These particles are referred to as silica particles 21. Then, coatedmetal sheet 50 was produced in the same manner as coated metal sheet 1except that silica particles 21 were used instead of silica particles 1as the gloss adjusting agent in the overcoat coating material.

Coated metal sheets 49 and 50 were evaluated for flat portion-corrosionresistance in accordance with the aforementioned two-cycle method. Thebase sheet type, the gloss adjusting agent type, the matting agent type,R1, R2, D1_(97.5), D2_(97.5), the cut value, the particle diameter R1′of the main component of the silica particles added, T, the content ofthe gloss adjusting agent, the content of the matting agent, the contentratio of two types of silica particles, and evaluation results of flatportion-corrosion resistance of coated metal sheets 47, 49, and 50 areshown in Table 7.

TABLE 7 Gloss adjusting agent Matting agent Flat portion- Over- Con-Con- Primary corrosion coat Cut tent Con- tent particles/ resistanceBase T R1 D1_(97.5) value (vol tent R2 D2_(97.5) (vol D2_(97.5)/Microporous 1 2 No. sheet (μm) Type (μm) (μm) (μm) R1′ %) ratio Type(μm) (μm) %) T particles cycle cycles 47 3 25 Silica 7 22 23.5 30.0 597.5/ Acrylic 35 50 5 2.0 Primary B B 18 2.5 1 particles 49 3 25 Silica7 22 23.5 30.0 5 97.0/ Acrylic 35 50 5 2.0 Primary B C 20 3.0 1particles 50 3 25 Silica 7 22 23.5 30.0 5 96.5/ Acrylic 35 50 5 2.0Primary B C 21 3.5 1 particles

Reference Experiment 3

Coated metal sheet 51 was produced in the same manner as coated metalsheet 48 except that the overcoat coating material for coated metalsheet 48 was treated with a roller mill under conditions for pulverizingsilica particles F before the matting agent was blended. Then, coatedmetal sheet 51 was evaluated for flat portion-corrosion resistance inaccordance with the aforementioned method, and graded B both in theone-cycle test and the two-cycle test.

As clear from Table 1 to Table 4, coated metal sheets 1, 4, 6, 10, 13 to16, 20 to 22, 26 to 29, and 32 to 41 all have designability of a mattegloss, have sufficient processed-part adhesiveness and scratchresistance, and additionally have flat portion-corrosion resistancecorresponding to 10 years of actual use.

In contrast, coated metal sheets 2, 3, 8, and 9 had insufficient flatportion-corrosion resistance. It is conceivable that coated metal sheets2, 3, 8, and 9 had insufficient flat portion-corrosion resistancebecause the gloss adjusting agent was exposed from the overcoat coatingfilm during the resistance test due to optical degradation of theovercoat coating film.

Furthermore, the coated metal sheets 7, 11, 12, and 25 had an extremelyhigh gloss, and the intended designability (matte feeling) could not beachieved. Thus, it was determined that coated metal sheets 7, 11, 12,and 25 did not deserve to be subject to evaluation test of flatportion-corrosion resistance, and the evaluation test was not conducted.It is conceivable that coated metal sheet 7 had an extremely high glossbecause the film thickness of the overcoat coating film was extremelythick, that the coated metal sheet 11 had an extremely high glossbecause the particle diameter of the gloss adjusting agent is extremelysmall, that the coated metal sheet 12 had an extremely high glossbecause the content of the gloss adjusting agent was too low to adjustthe gloss, and the coated metal sheet 25 had an extremely high glossbecause the content of the matting agent was too low to adjust thegloss.

Additionally, coated metal sheet 5 lacked concealability. In otherwords, the visibility of the overcoat coating film was developed only tothe extent where the substrate of the overcoat coating film (undercoatcoating film) was visually observed, and the intended designabilitycould not achieved. Thus, it was determined that coated metal sheet 4did not deserve to be subject to evaluation test of flatportion-corrosion resistance, and the evaluation test was not conducted.It is conceivable that the reason why the above-described concealabilitywas insufficient is that the film thickness of the overcoat coating filmwas extremely thin as well as the particle diameter of the glossadjusting agent was extremely large relative to the film thickness T ofthe overcoat coating film.

Alternatively, coated metal sheets 17, 18, 23, 30, and 31 hadinsufficient processed-part adhesiveness. Thus, it was not possible toconduct evaluation test of flat portion-corrosion resistance. It isconceivable that coated metal sheets 17 and 18 had insufficientprocessed-part adhesiveness because the content of the gloss adjustingagent in the overcoat coating film was extremely high, that the coatedmetal sheet 23 had insufficient processed-part adhesiveness becauseD2_(97.5)/T was extremely large, and that the coated metal sheets 30 and31 had insufficient processed-part adhesiveness because the content ofthe matting agent in the overcoat coating film was extremely high.

Alternatively, coated metal sheets 5, 19, and 25 had insufficientscratch resistance. Thus, it was not possible to conduct evaluation testof flat portion-corrosion resistance. It is conceivable that coatedmetal sheet 5 had insufficient scratch resistance because the filmthickness of the overcoat coating film was extremely small, that thecoated metal sheet 19 had insufficient scratch resistance because theparticle diameter of the matting agent is extremely small relative tothe film thickness T of the overcoat coating film, and that coated metalsheet 25 had insufficient scratch resistance because the content of thematting agent was extremely low.

Additionally, coated metal sheets 32 and 33 both exhibited the intendeddesignability (matte) irrespective of the type of the base sheet(configuration such as whether the undercoat coating film is included ornot) as well as had sufficient processed part-adhesiveness, scratchresistance, and flat portion-corrosion resistance. It is conceivablethat this is because flat portion-corrosion resistance is provided bythe overcoat coating film.

Additionally, both coated metal sheets 38 and 39 all exhibited theintended designability (matte) irrespective of the type of the glossadjusting agent as well as had sufficient processed part-adhesiveness,scratch resistance, and flat portion-corrosion resistance. It isconceivable that this is because even particles having micropores, ifnot exposed from the surface of the overcoat coating film, would exhibitsufficient flat portion-corrosion resistance, whether the particles areinorganic particles or organic particles.

Coated metal sheet 40 also exhibited the intended designability (matte)irrespective of the type of the matting agent as well as had sufficientprocessed part-adhesiveness, scratch resistance, and flatportion-corrosion resistance. It is conceivable that this is becauseprimary particles would exhibit sufficient flat portion-corrosionresistance, whether the particles are inorganic particles or organicparticles.

Also as clear from Table 5, coated metal sheet 34 had more excellentflat portion-corrosion resistance than coated metal sheet 15, which hadthe same configuration other than having a chrome-free base sheet. It isconceivable that this is because anti-rust treatment of the base sheetwith chromate has improved the corrosion resistance.

The coated metal sheet 41 also exhibited excellent results in anyevaluation. It is conceivable that this is because coated metal sheet 41has an intercoat coating film and thus is provided with designabilityand functionality from the intercoat coating film, and that, as aresult, more excellent properties than the designability andfunctionality exhibited singly by the overcoat coating film have beenexhibited.

Also as clear from Table 4, coated metal sheets 34 to 36 all maintainflat portion-corrosion resistance for a period longer than coated metalsheet 15. It is conceivable that this is because base sheet 4 in coatedmetal sheets 34 to 36, which contains a chromate-based anti-rust pigmentin the undercoat coating film and of which plated steel sheet has beensubjected to chromate anti-rust treatment, exhibits higher corrosionresistance than that of base sheet 3 in coated metal sheet 15 for a longperiod.

Also it is obvious from Table 6 and Table 7, it can be seen that thegloss adjusting agent has no substantially adverse influence on the flatportion-corrosion resistance of the coated metal sheet even if particleslarger than 0.9T are contained, provided that the content of theparticles is at least 2.5 vol % or less relative to the particles having0.9T or less and that the particle diameter of the particles is 1.2times (1.2T) or less the film thickness of the overcoat coating film. Itis conceivable that this is because particles slightly larger than thefilm thickness T of the overcoat coating film are likely to be orientedsuch that their long diameter is along the direction in which theovercoat coating material is applied and, if in a small amount, will besufficiently and continuously covered with the resin of the overcoatcoating film for the intended use period.

The gloss adjusting agent may also contain large particles which may bedetected in a position deviating from its particle size distribution(coarse particles), although in a small amount. It is conceivable thatsuch coarse particles, as clear from Table 6, are exposed from theovercoat coating film in durable use to cause impairment in the flatportion-corrosion resistance of the coated metal sheet. However, whenthe overcoat coating material containing the above-described coarseparticles is subjected to an appropriate pulverizing step, a coatedmetal sheet having sufficient flat portion-corrosion resistance can beobtained. It is conceivable that this is because the above-describedcoarse particles are finely pulverized in the overcoat coating materialto a degree enough for the coated metal sheet to exhibit the intendedportion-corrosion resistance.

This application is entitled to and claims the benefit of JapanesePatent Application 2014-164265 filed on Aug. 12, 2014, the disclosure ofwhich including the specification, drawings and abstract is incorporatedherein by reference in its entirety.

INDUSTRIAL APPLICABILITY

In the coated metal sheet according to the present invention, reductionin the corrosion resistance in the flat portion, attributable toexposure, collapse and fall-off of the gloss adjusting agent andexposure, cracking, collapse, and fall-off of the matting agent from theovercoat coating film, is prevented. Thus, a coated metal sheet thatexhibits the intended appearance and corrosion resistance for a longperiod can be obtained, even if used in an exterior application for along period. Accordingly, the present invention is expected to furtherprolong the life of coated metal sheets for exterior use and to furtherenhance its usage.

1. A coated metal sheet comprising: a metal sheet, and an overcoatcoating film disposed on the metal sheet, wherein the overcoat coatingfilm is composed of fluorine resin, wherein the overcoat coating filmcomprises a gloss adjusting agent which is particles having microporesand a matting agent which is primary particles, wherein a content of thegloss adjusting agent in the overcoat coating film is from 0.01 to 15vol %, wherein a content of the matting agent in the overcoat coatingfilm is from 0.01 to 15 vol %, and wherein the coated metal sheetsatisfies the following equations:D1_(97.5) /T≦0.9Ru≦1.2TR1≧1.00.5≦D2_(97.5) /T≦7.03≦T≦40 wherein R (μm) is a number average particle diameter of the glossadjusting agent, T (μm) is a film thickness of the overcoat coatingfilm, D1_(97.5) (μm) is a 97.5% particle diameter in an accumulatedparticle size distribution of the gloss adjusting agent based on thenumber of particles, D2_(97.5) (μm) is a 97.5% particle diameter in anaccumulated particle size distribution of the matting agent based on thenumber of particles, and Ru (μm) is an upper limit particle diameter ina number particle size distribution of the gloss adjusting agent.
 2. Thecoated metal sheet according to claim 1, wherein the Ru is less than T.3. The coated metal sheet according to claim 1, wherein the metal sheethas been subjected to non-chromate anti-rust treatment, and the coatedmetal sheet is chromate-free.
 4. The coated metal sheet according toclaim 1, wherein the metal sheet has been subjected to chromateanti-rust treatment.
 5. The coated metal sheet according to claim 1,wherein the gloss adjusting agent is silica particles.
 6. The coatedmetal sheet according to claim 1, further comprising an undercoatcoating film between the metal sheet and the overcoat coating film. 7.The coated metal sheet according to claim 6, further comprising anintercoat coating film between the undercoat coating film and theovercoat coating film.
 8. The coated metal sheet according to claim 1,wherein the overcoat coating film is composed of a resin component, asthe main component, comprising polyvinylidene fluoride and acrylicresin.
 9. The coated metal sheet according to claim 1, having aglossiness at 60° is 0.1 to
 15. 10. The coated metal sheet according toclaim 1, being a coated metal sheet for exterior use.
 11. An exteriorbuilding material comprising the coated metal sheet according toclaim
 1. 12. A method for producing a coated metal sheet comprising ametal sheet and an overcoat coating film disposed on the metal sheet,comprising the steps of: applying an overcoat coating materialcontaining a fluorine resin, a gloss adjusting agent, and a mattingagent onto the metal sheet; and curing the coating film of the overcoatcoating material to form the overcoat coating film; wherein a content ofthe gloss adjusting agent in the overcoat coating film is from 0.01 to15 vol %, and a content of the matting agent in the overcoat coatingfilm is from 0.01 to 15 vol %, wherein the gloss adjusting agent isparticles having micropores, and the matting agent is primary particles,and wherein the gloss adjusting agent and the matting agent whichsatisfy the following equations are employed:D1_(97.5) /T≦0.9Ru≦1.2TR≧1.00.5≦D2_(97.5) /T≦7.03≦T≦40 wherein R (μm) is a number average particle diameter of the glossadjusting agent, T (μm) is a film thickness of the overcoat coatingfilm, D1_(97.5) (μm) is a 97.5% particle diameter in an accumulatedparticle size distribution of the gloss adjusting agent based on thenumber of particles, D2_(97.5) (μm) is a 97.5% particle diameter in anaccumulated particle size distribution of the matting agent based on thenumber of particles, and Ru (μm) is an upper limit particle diameter ina number particle size distribution of the gloss adjusting agent. 13.The method for producing a coated metal sheet according to claim 12,wherein the overcoat coating material has been subjected to treatmentfor pulverizing the particles in the overcoat coating material.